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Discussion Starter · #1 ·
Thought I would come here for a little direction on this. I have a 97 K2500 suburban with the 7.4L. It has a small starting problem. I can leave it parked for a day or 2 weeks and when I get in, it starts almost immediately. I can drive it somewhere (usually not far its just a weekend warrior) and it reach operating temp, cut it off, run in a store or sit at my kids soccer game, get back in and it turns over numerous times before it starts. I initially though fuel problem and it does have a new delphi fuel pump, not sure what was in it before I installed this one. But the fuel pump made no difference. Here is where I am kind of stumped. I though pressure regulator. For it to lack fuel it would be for several reasons, an internal leak, external leak, leak back into the tank, or weak pump. If it is any of these it would seem that logically with a leak, the longer it sits, the harder the start. This is the opposite. The longer it sits, the better it starts. It seems to only happen when I drive and turn it off for short time periods that its hard to start. Any suggestions on what to look for? I did run some fuel pressure tests but its been awhile and I don't remember the numbers and should do it again. I might have time today to do it. I do remember sometimes if falling below what it should be but I also remember with the lower readings, it didn't seem to start any different than with a higher reading. Thanks in advance
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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New pump doesn’t always mean good. I’d double check the pressure numbers.

I bought a new Bosch for my ‘95. The previous pump was failing, so I put the Bosh in. Theee days later it was only delivering ~4 psi when it should have been 14.

I bought one for a ‘96 Vortec and never looked back.
 
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Discussion Starter · #3 ·
I did check pressures today. It goes to 55 before start and ranges from 50 to 55 at idle. I can accelerate and it goes to about 61 or 62 then when I let off she drops back to 50. Seems the pump would be good reaching 62. I also checked fuel trims today. LT runs about 9 on 2 and 11 on 1. ST is at or near 0. I can accelerate to about 2,000 - 2300 rpm and LT comes down to about 2 and 3. I’ve read where the higher LT at idle that returns to 0 at higher RPM can signal just a small vacuum leak. The interesting thing was I turned it off and on numerous times. Each time I turned the key back on the pressure would go to 55 or 56. There was a few times where the pressure never changed when I turned the key back. It would be at 50 and when I turned the key on it would stay at 50. Interestingly enough it started fine every time while running these checks. I’m still leaning towards either fuel pressure regulator or even leaking injector. Just has me a bit stumped I’d like to pin point what it is before I start throwing parts. But then at its age I’ve considered new injections, rails and pressure regulator. Considering the plenum and all have to come off to do any of those might be just as well to do them all
 

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I would guess an injector that's leaking.
As soon as you turn it off, the faulty injector is spraying; not long the engine is flooded.
Let it sit over night, the leaking drains the fuel rail and there is enough time for the flooded areas to drain/dry.
 

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Discussion Starter · #5 ·
That makes sense and would explain why the longer it sits the better it starts. Do any of those injector cleaner additives actually work or at this point would new injectors be the fix?
 

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I'd try a cleaner first.
Are you using a Top Tier gas (google for a list of companies), they have injector cleaners in the gas?
 

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Discussion Starter · #7 ·
I'd try a cleaner first.
Are you using a Top Tier gas (google for a list of companies), they have injector cleaners in the gas?
Actually probably not very often. I usually fill it up right down the road from the house and that’s an unbranded gas station. I’ll check the list you are talking about and see what I find
 

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I agree on the leaky injectors. I had same problem. Changed out the injector spider with aftermarket system (you can’t get individual injectors) and it ran great. Mine was a 96, I assume same system. It’s an afternoons work and not inexpensive but well worth it. I must have put three pumps in there thinking I had fuel pressure issue.
 

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Discussion Starter · #10 ·
I agree on the leaky injectors. I had same problem. Changed out the injector spider with aftermarket system (you can’t get individual injectors) and it ran great. Mine was a 96, I assume same system. It’s an afternoons work and not inexpensive but well worth it. I must have put three pumps in there thinking I had fuel pressure issue.
This is the 7.4 vortec with multi port. I can but individual injectors but wouldn’t do that. I’ll replace all 8. I’m pretty convinced now that’s what it is
 

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2001 GMC Sierra SLE 2500HD , AT , 6.0 , 4x4 extra cab
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Logic says related to heat / warm .
Check temp sensors & connections - use temp test tool , see what the temp sensor spec.s are voltage & resistance , put you own signal to computer [ do this if you know the system - you could kill it ] , different things work / or not at different temps - your cold start system works , so look for normal hot start causes - example in the old carb days - the choke may stick in the on position - hot start issues - rich running .
If the sensor circuit sends a always cold - the injectors spray more for a cold start .

Another issue - electrical failures & mechanical issues , heat / expand , cold / shrink .
 

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Thought I would come here for a little direction on this. I have a 97 K2500 suburban with the 7.4L. It has a small starting problem. I can leave it parked for a day or 2 weeks and when I get in, it starts almost immediately. I can drive it somewhere (usually not far its just a weekend warrior) and it reach operating temp, cut it off, run in a store or sit at my kids soccer game, get back in and it turns over numerous times before it starts. I initially though fuel problem and it does have a new delphi fuel pump, not sure what was in it before I installed this one. But the fuel pump made no difference. Here is where I am kind of stumped. I though pressure regulator. For it to lack fuel it would be for several reasons, an internal leak, external leak, leak back into the tank, or weak pump. If it is any of these it would seem that logically with a leak, the longer it sits, the harder the start. This is the opposite. The longer it sits, the better it starts. It seems to only happen when I drive and turn it off for short time periods that its hard to start. Any suggestions on what to look for? I did run some fuel pressure tests but its been awhile and I don't remember the numbers and should do it again. I might have time today to do it. I do remember sometimes if falling below what it should be but I also remember with the lower readings, it didn't seem to start any different than with a higher reading. Thanks in advance
I had a similar situation. I don't remember the details. I changed the crank shaft position sensor and it fixed the problem. It was easy to change myself with directions I got from searching Youtube videos. Good Luck!
 
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