Quick and easy fuel pressure test (gm tbi)
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- čas přidán 12. 06. 2019
- 1995 gm tbi fuel pressure test with OTC's 4480 fuel pressure kit. In about 10 minutes we diagnosed a faulty pump without guesswork.
Link to actual tester
www.amazon.com/gp/product/B00...
Thanks for taking the time, it is appreciated. Good informative video--keep up the good work.
Appreciate the kind words William!
Awesome hack man! Thank you for taking the time to make and post this! I've got a 92 suburban c1500 that has been hestitaing. Got code 33. Gonna try this.
Was it your fuel pump? I have code 33 also
Just watched this, everything was spot on. Only thing I would correct is the pressure ratings. TBI’s like 10-13psi. But this was a slick way of checking pressure. Thanks for that!
Appreciate it man. For some reason all the new pumps I've installed (delco, denso, delphi) have increased pressure....I understand that the pump doesn't create pressure, it's the restriction that does that, which would be the regulator in this application, but nonetheless they've all had 15-20 after replacement. Ecu seems to maintain the block learn for stoic operation at least.
Someone in the comments said these don't have a check valve in the pump. All of the dozens of them I've don't here, after the new pump they'll hold pressure for hours.
Thanks very much for the clear, concise explanation. That helped me a bunch. I'm trying to diagnose a 1995 GMC Safari 4.3 with TBI. Going nuts trying to figure out where to hook my pressure guage. Now I know!
You're very welcome! Best of luck to ya!
@@PSBEadventures hey man what’s that wire connected to your obd 1 plug I have the same scanner but with my 90 gm it doesn’t turn on when plugged in but I don’t have that wire on the side off the plug
@Sega 22 that is the power supply for the scanner. The other end is an alligator clip that hooks to the positive side of the battery.
@@PSBEadventures man I’m missing that I guess my scanner is useless
@Sega 22 I'd say you can grab one on ebay maybe
Great video by a master mechanic!!!!
Don't know about the master part but appreciate the kind words!!!
@@PSBEadventures like you brother I've been around the block a few times and I know when I'm listening to a man who knows what the hell he's talkin about. I know when somebody's blow and shit and I know when somebody knows how to turn a wrench and has been doing it for a long time and that makes you a Master!
@brt-jn7kg appreciate that man!
These are the exact problems I'm having!! Thank you!!
Anytime
Very helpful video, thanks
You're more than welcome man
Good job. I learned something.
Awesome! Thanks for watching!!!
Thanks for the vid.
That just goes to show you you can't beat those TBI Chevys!
Yeah they’re pretty sturdy built, definitely nothing for performance but its reliable. Realizing that now that I’ve got a 93 s10 2.8
good video my brother..
Appreciate that!
Thank you
My '88 V3500 SRW CC has a stock TBI 350. Lost spark and injector pulse. On my third distributor. Timing set with tan computer advance wire unhooked to 0-2 degrees of timing and locked down. Plugged timing wire back up and when running the computer is advancing the timing at idle about another 10 degrees (1" or so ahead of the timing tab / about 1o'clock on the balancer). Vacuum smoke test done with no leaks even when engine is ice cold and not run. Replaced spark plugs, ICM, IAC, temp sensor, MAP, and fuel filter. Tested the EGR valve to be like new and working. Swapped another identical ECM in to see if it would help and it made no difference. Ran exactly the same. Truck is "loading up" rich and has poor acceleration. Stumbles, etc. Put this exact test fitting on to check my pump and it primes to 11psi and when running goes to 21psi. Is this considered good? Anyone have any other ideas of what might be wrong with my truck? Thanks!
Did you ever figure out the issue?
@@jasonfalk1586 I replaced both fuel pumps and now have zero issues. Went with new fuel tanks as well while I was making the repairs. Runs great now. Tank selector valve, etc. also works beautifully.
Success!! Cut the hole through the floor of my 89 suburban and a $20 fuel pump later I have a new vehicle! At least now I know it wasn't the ingition timing, leaking brake booster, clogged injector screens, fuel filter, PCV valve, MAP sensor, O2 sensor, or throttle position sensor, since I've already replaced those! 😂 Thank you so much for putting good information on the Tube!!
Glad to hear it and glad to help!
My TBI engine idles okay but sounds like it wants to bog for half a second after pressing the throttle.
It also sputters and misfires around 3.5k RPM, and it doesn't rev any higher (pressing the throttle harder only creates a worrying loud hum in the engine). It occasionally revs up to the 4.7k RPM ECU limiter if I double the amount of gasoline for that RPM range in the ECU (6 air : 1 gas instead of usual 12 air : 1 gas).
From all that, I assume it's a lack of fuel/atomization problem (though the injectors jet cones look okay). The fuel pump sounds okay too, I inspected it and its connecting rubber hose and cleaned its filter (actually got rid of it and only left the "sock"), replaced the main fuel filter, all with no change in the symptoms. I also tried restricting the fuel regulator more, to increase the pressure, with no change in the symptoms either.
I replaced spark plugs and cables; those did make a difference because the sputtering appeared at 2.5k RPM before.
Can a fuel pump sound okay yet perform poorly? Even with 6psi at the injectors, the engine in this video sounds way better than mine when revving.
@@soupflood you put a gauge on it?
@@PSBEadventures no, I didn't measure the fuel pressure
@soupflood get you a base measurement when driving under acceleration as well. Just because all those parts are new doesn't mean they are good. It's kinda like the Dr guessing you have high blood pressure and giving you medicine for it without ever measuring it. Invest in a good gauge and you'll have it forever. This truck in this video had an engine replacement for lack of power before it came here. Still no power with a new engine. Imagine how much cheaper a fuel gauge would have been! The most expensive snap on gauge and most expensive fuel pump still wouldn't be close to an engine
my 91 camaro RS 5.0 has had this happen 3 times the hose in between the pump and sending unit dries out and leaks probably due to ethanol in fuel next time I will have a plastic hose over the fuel line to protect it or use an ethanol fuel line
I’ve got a 90 Chevy 1500 right now that will not restart after a hot shutdown. No codes and the minute I pull the coil wire to check for spark I get spark and fuel out the injectors. The one time it wouldn’t start it didn’t have fuel out the injectors.
Watson is the man check him out in liberty sc at titan automotive fyi I've got two bricks with about 70 keys and 20 or so adapters if you ever need one
Awesome!
Im having a similar problem with my 95 c1500, cold start will pickup a little bit but when she gets warm it’s so sluggish, like I’m stuck going 25-30 in a 60 while slowly accelerating. And I’ll hit a decent hill going 60 and when I get to the top I’m going like 35
Yep, maybe should check that pressure! Hope the video helps man
This helps a lot I bought a fuel pressure guage and had it all wrong .
My truck problem is the engine i guess would say it lobes almost like a big cam makes one sound like then once ya get rolling it cuts out any thoughts would be welcome its a 95 4.3 liter engine 5 speed
If the fuel pressure is all good, I think those had issues with the distrbutor
Did you ever get resolved? I've got a 94k1500 5.7 manual.....
Stutters a little under 2k rpm through all gears.... once it hits about 2k rpm it smooths out....
I have a 91 s10 2.8 5speed. It has intermittent extended cranking, low power. Also has lugging under load that is harder the more throttle you give it. This lugging seems more pronounced as the outside temps become colder. Could this be caused by the tbi pressure regulator? Thanks
Very possible
@@PSBEadventures Thank you
Fuel pressure regulators are an issue with some of these right from the factory.
What model is that scanner? I have a 91 c1500 that I’m trying to work on.
That's called the snap on "brick"
By the way these tbi pressure regulators are factory designed to bleed off the pressure when shut off. No problem there.
New Delphi pump held pressure for over an hour! I think some of the very last gm tbi's may if had a check valve in the pump feed stem
Can you hookup that GM adapter up by the throttle body fuel line inlet - at the TBI unit? Instead of fighting the fuel leak at the filter?
Yes I believe that is where it is ment to be used actually.
Yes that particular adapter is meant to be connected at the throttle body but it will work at the filter, theres also one that installs in place of the filter its just a fitting with female ends & a schrader valve in the middle! now there are 2 different sizes of those actron brass tbi swivel adapters 7/16 & 1/2" depending on your fuel guage size!
Y install the tool fitting on the filter input? I realize it is inconvenient at the TBI. I presume the tool fitting is directional.
Yep, just easier. The fitting at the throttle body can be a pain to start. If it got crossed you'd be in a jam, at the filter the line is a ton more flexible. Fitting for gauge is male and female so just goes one way
Would low fuel pressure cause it to back fire? I have a 95 tahoe that back fires after a running long periods of time such as couple hour roud trips. Iv changed spark plugs, wires, engine temp sensor, 02 sensor, timing chain, fuel filter, map sensor. No codes at all.
Maybe. Also, the magnets inside the distributor can crack and cause a backfire.
I just rebuilt my throttle body on a Chevy G20 Sportsvan. One injector is splurting out gas everywhere and the other has big drops coming out. Would I test my fuel pressure the same way ? It's a 350 V8
Yes, and you can test it there at the tb as well. Sounds like you may have a regulator (the one in the tb) issue or bad injectors. They should have a fine, even mist, at idle that increases with throttle position.
Happen to know the part number for the o-rings that go onto the line at each end pf the filter?
Sure don't, Maybe grab a metric set of the nitrile ones
Whats up bud ... i did the same test and followed step by step what ya did and the pressure came up to 50 PSI ... thats way high ... would a bad fuel pump would do that ? Or any ideas or recommendations. Thank you
No
Sorry, just saw this, 50psi on tbi is way high, are you sure yours is tbi and not port fuel injection?
Would it be possible to flip the adapter and check pressure on the out side of the filter?
Possibly, you can check it at the throttle body as well
Mine does the same thing. Has about 9 at idle drops to 6 at rev. Truck idle good. Drives pretty good too with occasional jerking. 02 reads lean most of the time except for decel. Truck won't restart after a heat soak unless I unplug ect sensor. That's the weird part. I just think maybe injector pulse width giving it enough extra but it drives the same as it should like that so idk. The waveform also looked good to me for the pump and was between 3 and 4 amps. IDK.
I'd put my money on the pump for sure. Get you a good quality delco or delphi and ride!
Your pressure at the filter drops to 6 when you rev it?
@@PSBEadventuresdelphi fuel pumps are junk.they only last for 2 yrs
@dp1651 I own a full service repair shop and have used them for 15 years. I've yet to have a single one fail. They may be junk today, but those weren't. I see them riding all over town still. I will say ebay and Amazon do sell clones that say they are name brand, but are fake. Denso is definitely a better brand but they don't offer them for many domestic vehicles. I can only tell you my experience, I'm not here to tell you what brand fuel pump to use, only a recommendation.
@@PSBEadventures back then they were good not today Delphi fuel pump.why there is lifetime warranty on them they don't last.tryin a factory ac delco pump now.
So my 1995 k1500 runs good for about 40 min and then all of a sudden stumbles and backfires while driving. I turn it off for a bit, then continue driving and it does it all over again, any ideas what it might be?
Tough call there. I know that particular year has issues with the ecu. You can hit it moderately with the plastic end of a screwdriver to see if it stumbles while tapping it. Hate to go straight for the ecu, but cutting it off and back on resets it maybe.
I've got a 1987 K5 Blazer 350 TBI starts when you prim with fuel then dies ,any help would be greatly appreciated. It stopped running while driving and pulled it home,fuel pump makes noise when you turn the key on ,also checked wire at injectors plug and have power to injectors but injectors never spray fuel on there own.could it be bad injectors?
I'd want to see what the pressure is for starters. The pump has a rubber hose in the tank that can split, it will run but not pump to the injectors. You need at least 12-13psi to run good
Check ignition module. It sends spark signal to the ECM. When they fail, the ECM won’t pulse the injectors. Mine had that issue. Easy fix.
Thank you it was the ignition control module inside the distributor I fixed it three weeks ago
I’m running into that issue as well, I replaced my injectors and fuel filter and took apart and cleaned out my TBI
@@chandapollock7044 it ended up being the module inside the distributor it controls all of that
I heard what you said but it was at 8 lbs witch you were surprised what should a brand new top-of-the-line fuel pump run pressure didn't never say that I remember what am I looking for minimum to maximum
12-13psi should make it run good, should not drop off at all on accel
Hey there good video I'm having same problems with my truck. Pressure drops when I rev it but when I pinch the return line pressure guess up to 40psi. Would that still be a bad pump?
It could definitely be the pump just not supplying enough fuel. The pressure is just restriction to flow. If it's pretty normal pressure at idle or even slightly low pressure at idle and it drops off while revving, I'd say the pump would be at fault. There is a pressure regulator built into the throttle body that can go bad, but it generally makes them idle and run terrible
@@PSBEadventures great thanks for the advice. I'll start with the pump then
From what I’ve read and seen the pressure should approximately double when you pinch off the return line if the pump is good. Where are you pinching off the line. I need to pinch off mine and do the same test. My issue is a lean only after hot soak. Guessing it a vaccum leak or bad pump hose inside my tank. Usually my fuel pressure check is inconclusive because I’m checking at a time it’s not having the issue thus why a dead head check might tell the truth. I also know a bolt is broken off my head to exhaust so in theory that could be my issue but it ran fine that way long ago.
would there be any reason why my truck doesnt stay running after hooking up the gauge ??
Leaking maybe? Tee blocked off somehow?
Can you install the tester on the fitting on the back of the tbi unit? Does it have to be at the filter
You can. No problem at all.
The return line is in the way on my 90 silverado
@@mattmarshall1698 then install it where the fuel filter is
On my chevy silverado 1994 1500 5.7 I changed fuel pump,fuel injectors rotor cap,EGR valve fuel pump relay,TBI,idle control sensor,fuel filter,coil
When I drive for 20 mins my truck looses power and wants to shut off while I drive down the highway also when I get home and park I slightly press on the gas pedal the rpm jumps from 1 to 2 while keeping that acceleration if anyone have any idea of what it could be please let me know
Maybe throttle position sensor
How did you know it wasn't a weak spring in the pressure regulator?
I was checking it right out of the pump and also pinched off the return, still no pressure
I have never seen a pressure regulator cause low pressure, just leak
I have one doing the opposite. No misfires but runs rich, no power, and very poor fuel mileage. No codes. Gonna swap the o2 and then go from there. I'll check fuel pressure next
Rich definitely can be the o2, coolant temp reading too cold or a MAP. Fuel pressure regulator in the tb typically causes low pressure but could make it go up if there is a restriction. Let me know!
@PSBEadventures o2 seems to have fixed it. Haven't drove it much, but just from the smell alone, it's not super rich anymore or black smoking. Odd that it didn't have a engine light for it but I guess those OBD1 ecus with only a single wire o2 was very crude back in the day.
@c117ls7 good news. On the early obd1, it's gotta be just about not working at all to set a code. The older the system, the more the o2 will effect the mixture.
Would it cause lack of power when it gets hot? My truck starts and runs fine when cold. After it warms up it, say on my 15 min commute to work, I’ve got very little power to merge. Takes a while to jump from 55-70 mph
Absolutely worth checking the pressure.
@@PSBEadventures thank you. I’ll have to get the part. I’m at 293k miles. Trying to keep her alive as long as I can lol
@@SirGuidemere91 did you find out your issue? I’m having the same problem with my 91 s10 blazer
@@christhomas9470 no my pressure was fine. Another thing I was told was possibly the coil is getting hot or the plug wires need to be changed.
@@SirGuidemere91 that sucks, hopefully one us finds the issue..the search continues..😂😂😂
Nice that fitting didn’t come with the cheap hf kit ,and to u migiver to make one
It does though
First that is an OTC kit not HF! secondly that particular GM Tbi adapter is meant to be used at the throttle body, now there is also another adapter for the Tbi that you put in place of the fuel filter but either way works its just what ever floats your boat ✌
What is the prime pressure and run pressure supposed to be?
Usually around 10-15psi for both is normal. New pumps bought these days may run as much as 20psi
what is the correct fuel pressuere on that tbi engine (two inyectors)
Manual says 12-20psi
@@PSBEadventures '90 and newer is up there, my 88 calls for 10-13psi
Sorry to hijack the thread but I just want to say this on record. Thanks for all you mechanic and guys and range Turner's on CZcams. Just CZcams University myself through a full TBI rebuild and thanks to you project stock bottom end I got my fuel pressure tested with no problems. Time to put another 148k on this 88
7.4l 26-32 psi
120 for the kit, useless if ya already have the kit with out it.
try here for the single piece,
AN Fuel Pressure Adapter - Part Number 400200-BL (400200BL) by Mr.Gasket.
My pressure is about 7-8 and when I turn the key (crank the car ) the pressure drops slowly as I keep cranking then goes back to normal pressure (7-8) when I stop cranking car …. Any ideas I’m stomped
Keep the gauge on it and go drive it under heavy acceleration. If it drops any during acceleration it needs a pump or regulator
@@PSBEadventures I can’t even drive it anymore at first I could crank it with my foot on the gas and it would run until I took my foot off the gas , but now the pressure drops to zero whenever I try to crank the car and sometimes will jus jump up to 4 psi then drop right off even , I’ve also changed the regulator today and that didn’t change anything
@@boofboikarti3235 gotcha. Sounds like it's time for a pump
I have a 94 k2500 and its running great until it warms up and then the idle gets a lil rough, and it feels like it should have more power, I have changed almost everything except the fuel pump and injectors, would the fuel pump lose power after it warms up if its getting ready to go out and would that make it run rich, Thanks in advance
I think it would tend to run lean after hot in my opinion unless the regulator is failing maybe. Anything is possible for sure. A good test like this one may be really helpful. Distributors fail and affect timing when warm, also the ecu in that year have been prone to fail but usually they cause a no start after warm.
@@PSBEadventures Thank you for the reply, I'm most likely going to change the pump anyway because I just bought the truck it has 190,000 and I dont know if its ever been changed and the other things you mentioned are really helpful as well, Great video btw and thanks again
@Mercedes L Indigenous cool deal. Delphi makes a nice entire drop in assembly with sending unit and all for a good price. We use them or Denso here at the shop a ton with really good success
@@PSBEadventures Will do, I was looking into the fuel pumps and I will take your recommendation and go with Delphi, Thank you for taking the time and caring enough to respond, your a real one, I'll let you know if it fixes it
@@mercedeslindigenous4219 anytime!
See here’s the issue with my 90 7.4. It’ll start everytime. Sounds like it’s cammed though. Will blow black smoke on a good day. I’ve replaced the map sensor egr valve and egr solenoid not one change. Still does it.
Sounds like it's too rich. If something is forcing the egr open, that will make it do that for sure. Unhook the vacuum line to it idling and see if it changes. At idle there should not be vacuum to the egr valve diaphragm
@@PSBEadventures so vaccum will cause the egr to open right?
@@PSBEadventures at idle the diaphragm should be closed correct?
@@PSBEadventures also not one check engine light is on.
@@chrisperry1756 correct, you can take the valve off and block that port off and see if it changes it as well
Dam i think this is whats wrong with my 91 k1500 it feels slow!!! Ive been driving the truck for 8 years and it alwayd felt slow last year it started to get worse the truck turns off when you driving slow
I bet so man! It's age now more than anything.
Thank you. Just trouble shooting a 91 Chevy truck. No start. Could hear fuel pump. But sounds like it was draining back to the tank. And psi was 0. When on. And crank.
There's a rubber section of pipe between the motor part of the pump and the hanger, it may be split. Seen it before
@@PSBEadventures 100% sure it is. Have to fix a No crank now then replace pump. Was going to remove bed? But might just drop tank
9lbs is OK for a tired truck 12 to 13 from factory unless it's a 454 94-95 then it's 30 psi
Yep. All the new Delco and Delphi pumps we install here at the shop are always around 15-20 for some reason. So far the ecu's have been able to moderate the block learn and customers have reported good results, fuel mileage, etc. I think they run way better with a touch more pressure like that. Injector seems to atomize better.
Let's me know where to get a good fuel pump plz.
I use delphi from Rock Auto. The entire assembly with sending unit and all
The reason why I asked is because is my 3rd time dropping my tank do to this reason thank for replying,,
Delphi is junk not good quality.
Hello, great video. So, I hooked a fuel pressure set up exactly like the one you used on my,1995 GMC,1500 with a 5.7 motor. My test gauge said " 0" ?
So I then hooked up a Mr.Gasket fuel pump gauge, Same results "0" ! The truck runs but lacks power. The truck doesn't miss, overheat, die out ,etc. In fact it idles very good. I have changed ECM and the Idle control valve. What di you think? Thanks for your time
If you have it hooked up just like this on the filter side and it reads zero, it's a miracle its running! I have seen them run with as little as 4 or 5 pounds. Sounds like it's time for a pump
11 psi is normal I think
Yeah, 11-12 psi is what they usually run. This new Delphi pump gave it around 20 and man did the truck run like new!
@@PSBEadventuresl put a Delphi fuel pump in my truck two yrs ago.its bad and weak 5psi at idle.sure don't last at all.its just went out my fuel pump.l have the actron fuel gauge with this adapter.
@dp1651 my guess would be its just like everything else. Quality control has went by the wayside, especially when the qc man was working from home during the virus
these fuel systems equalize almost instantly, theres no """chet balve"" in the fuel pump .. that truck has a weak pressure regulator spring or leaking diaphram.
Lol, a fuel pump fixed the vehicle. And there is 100% a "check valve" in the pump. Without the valve the pump would have to prime itself every start up. Every electronic in tank fuel pump gm has ever used as far as I know has a "chet bave" but what do I know....I guess the pump mysteriously fixed those parts you said were bad. Thanks for the comment tho
@@PSBEadventures pump DOES NOT have a chet balve! the pump primes as soon as the key is turned to run.
Sure thing! I just started working on cars a couple days ago. Sorry for the confusion.....🤕
@@PSBEadventures only the newer higher " pressure " systems have the " chet balbe".. the fuel pressure regulator sets the pressure in the older tbi systems.
@@PSBEadventures what was the pressure after installing the fuel pump?
normal pressure
For a worn out pump. Ran like it had nitrous with the new pump. Pressure drop with load and acceleration is not normal.