97 454 L29 Long Crank

[TN454K3500]

My truck fires up good when cold, but when it's hot it can have a long crank after sitting. If you turn the truck off then turn the truck back on (within ~10 mins) it fires up immediately, just like when it's cold. If it sits for ~30 mins, then it has a long crank. If you barely give it some gas while starting it then it will fire right up like it should.

I have recently replaced tank fuel pump, transfer fuel pump, injectors (precision auto injectors), FPR, FPR vacuum hose, distributor, distributor cap/rotor, plugs and wires. Part of it was to try to mitigate this issue and part was due to other reasons. It did this BEFORE and AFTER these changes, basically no change to this particular issue.

I am going to do some testing with the fuel pressure to see If I loosing fuel pressure in the rail somehow, but it just doesn't make sense how it starts up so good when it's cold.

Just throwing it out there to see if someone has had this issue before or if there is some vacuum lines or something that could cause this....

Thanks

 

[HotWheelsBurban]

My truck fires up good when cold, but when it's hot it can have a long crank after sitting. If you turn the truck off then turn the truck back on (within ~10 mins) it fires up immediately, just like when it's cold. If it sits for ~30 mins, then it has a long crank. If you barely give it some gas while starting it then it will fire right up like it should.

I have recently replaced tank fuel pump, transfer fuel pump, injectors (precision auto injectors), FPR, FPR vacuum hose, distributor, distributor cap/rotor, plugs and wires. Part of it was to try to mitigate this issue and part was due to other reasons. It did this BEFORE and AFTER these changes, basically no change to this particular issue.

I am going to do some testing with the fuel pressure to see If I loosing fuel pressure in the rail somehow, but it just doesn't make sense how it starts up so good when it's cold.

Just throwing it out there to see if someone has had this issue before or if there is some vacuum lines or something that could cause this....

Thanks

Is the starter working as it's supposed to? How good and clean are the connections and terminals on the battery cables? Corrosion can be down under the insulation where you can't see it.
My Burb is a 5.7, but I had a similar issue a few years ago. What ended up fixing it, was to clean and retighten the connections on the cables, replacing the long positive cable that goes across the fan shroud and over to the back of the computer box. 8' long, and I had a battery/auto electric shop make it for me. Parts stores wanted big bux for this cable; this shop made it for under $15. The other thing I did, was drop the starter and clean it, there was oil and grunge in it. Then I checked the terminals on the solenoid, and the smaller one that goes to the ignition switch wire, was a little bit loose. I tightened it up with a small pair of vise grips, the solenoid on my truck doesn't have a regular hex nut holding this in place.
All this stayed working for the next 3 years, driving it every day. At that point the battery croaked and the starter was suspect. So I replaced both. New starter has a more positively engaging sound to it.

 

[Spareparts]

See if your fuel pressure bleeds off after sitting a little bit. If it does its most likely bad injectors. What is your fuel pressure?
They always start fine cold because it needs to be rich anyway so bad injectors just kinda help it.

 

[TN454K3500]

Is the starter working as it's supposed to? How good and clean are the connections and terminals on the battery cables? Corrosion can be down under the insulation where you can't see it.
My Burb is a 5.7, but I had a similar issue a few years ago. What ended up fixing it, was to clean and retighten the connections on the cables, replacing the long positive cable that goes across the fan shroud and over to the back of the computer box. 8' long, and I had a battery/auto electric shop make it for me. Parts stores wanted big bux for this cable; this shop made it for under $15. The other thing I did, was drop the starter and clean it, there was oil and grunge in it. Then I checked the terminals on the solenoid, and the smaller one that goes to the ignition switch wire, was a little bit loose. I tightened it up with a small pair of vise grips, the solenoid on my truck doesn't have a regular hex nut holding this in place.
All this stayed working for the next 3 years, driving it every day. At that point the battery croaked and the starter was suspect. So I replaced both. New starter has a more positively engaging sound to it.

I will say I believe it is, it cranks over "strong" or however you want to put it. It doesn't seem like it is struggling. As far as corrosion they are good in clean. The positive side has that spacer in-between the two hot wires that I replaced last year. However, this is def something I haven't double checked so it is a good idea and I will run through this.

Was your issue all the time or only when the vehicle was hot?

Thanks

 

[Schurkey]

Subscribing because my '97 K2500 7.4L does the same thing. Starts great cold, cranks a long time when warm. Opening the throttle seems to help--but maybe it's my imagination.

 

[TN454K3500]

See if your fuel pressure bleeds off after sitting a little bit. If it does its most likely bad injectors. What is your fuel pressure?
They always start fine cold because it needs to be rich anyway so bad injectors just kinda help it.

I am going to run the checks this evening. Can you confirm what fuel pressure should be?

I am starting to wonder if I installed the correct fuel pump. The old fuel pump had started to get to where it whined and I was worried it would go out. I ordered all the parts off RockAuto and when I got the pump out of my truck the tube configuration did not match what I had ordered.

This was the pump I had ordered - this was just going off year, make, etc...

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Below is what my pump looked liked, or really close. The vent tube (small non threaded one, was still a little different). I got on rock auto and searched around until I found configuration that matched (1995 K3500). I just assumed since my truck was a cab and chassis maybe it was different or rock auto had it incorrect. The one above there is no way the lines would fit correctly. This pump turns towards the cab, the one above turns away.

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I was just worried about the configuration but one thing I just noticed that is a big difference is the top pump is rated for 62 PSI and the bottom is 44 PSI. I was just happy when I found the right configuration that I just ordered it.

 

[someotherguy]

Yeah.. 1994-1995 7.4 is TBI but higher pressure than the earlier TBI trucks; the early ones are the same as a small block TBI at 9-13 psi. 1994-1995 7.4 TBI are 26-32 psi. Your 1997 Vortec 7.4 spec is 58-62 psi.

The pump you got rated at 44 psi is the big red flag, to me. The good news is, you can keep the sender you already got with the correct hard line setup, and just replace the pump. Double-check your pressure readings and applications before spending money but I'm betting the Delphi FE0114 (1996-1997 5.7, 7.4) is what you'll need.

Richard

 

[TN454K3500]

Yeah.. 1994-1995 7.4 is TBI but higher pressure than the earlier TBI trucks; the early ones are the same as a small block TBI at 9-13 psi. 1994-1995 7.4 TBI are 26-32 psi. Your 1997 Vortec 7.4 spec is 58-62 psi.

The pump you got rated at 44 psi is the big red flag, to me. The good news is, you can keep the sender you already got with the correct hard line setup, and just replace the pump. Double-check your pressure readings and applications before spending money but I'm betting the Delphi FE0114 (1996-1997 5.7, 7.4) is what you'll need.

Richard

Thank you for your information. I don't know how to tag multiple people in one post but to answer your question and @Spareparts question, here is the fuel pressure test I preformed. Your opinions would be greatly appreciated, but I think I have the wrong fuel pump....

Fuel pressure test:
Key turned hits 50 PSI
**did not purge line from air on test gauge**
Pretty quickly dropped to 45 PSI, within 5 mins
After 30 mins it was ~40 PSI
Key on started, cold, started immediately, 44 PSI exactly
Run 5 mins, 44 PSI, ~125 degrees, turn off pressure goes to 41 PSI immediately
Off 5 mins, pressure 41 PSI
Starts up fine, back at 44 PSI, Run 20 minutes
At 20 min mark, Temp ~ 190, 44 PSI
Off 25 minutes, 42 PSI
-10 min mark, 42 PSI
-20 min mark, 41 PSI
-25 min mark, 41 PSI
Started right up, turned off immediately and back at 42PSI

I know injectors have some allowable leak rate so I don't believe injectors are the issue here from the data I have....

Unfortunately I was not able to recreate the long start issue however I have a gut feeling it is engine temperature relative to trying to start with low fuel pressure. So when I give a lil gas it fires right up? Makes sense in my head at least. So much for trying to match what was on the truck when replacing parts.... live and learn

 

[BNielsen]

Subscribing because my '97 K2500 7.4L does the same thing. Starts great cold, cranks a long time when warm. Opening the throttle seems to help--but maybe it's my imagination.

I'm in the same boat, cold it'll start on the second revolution but warm it'll crank and crank, spit and sputter, finally catch and blow out a cloud of unburnt fuel.
I think @Mangonesailor said it's something in the PCM but your truck is still a black box isn't it?

Thank you for your information. I don't know how to tag multiple people in one post but to answer your question and @Spareparts question, here is the fuel pressure test I preformed. Your opinions would be greatly appreciated, but I think I have the wrong fuel pump....

Fuel pressure test:
Key turned hits 50 PSI
**did not purge line from air on test gauge**
Pretty quickly dropped to 45 PSI, within 5 mins
After 30 mins it was ~40 PSI
Key on started, cold, started immediately, 44 PSI exactly
Run 5 mins, 44 PSI, ~125 degrees, turn off pressure goes to 41 PSI immediately
Off 5 mins, pressure 41 PSI
Starts up fine, back at 44 PSI, Run 20 minutes
At 20 min mark, Temp ~ 190, 44 PSI
Off 25 minutes, 42 PSI
-10 min mark, 42 PSI
-20 min mark, 41 PSI
-25 min mark, 41 PSI
Started right up, turned off immediately and back at 42PSI

I know injectors have some allowable leak rate so I don't believe injectors are the issue here from the data I have....

Unfortunately I was not able to recreate the long start issue however I have a gut feeling it is engine temperature relative to trying to start with low fuel pressure. So when I give a lil gas it fires right up? Makes sense in my head at least. So much for trying to match what was on the truck when replacing parts.... live and learn

Yeah those pressures are super low, and to my knowledge good injectors shouldn't leak down any? I dunno, maybe I'm overthinking

 

[TN454K3500]

I'm in the same boat, cold it'll start on the second revolution but warm it'll crank and crank, spit and sputter, finally catch and blow out a cloud of unburnt fuel.
I think @Mangonesailor said it's something in the PCM but your truck is still a black box isn't it?

Yeah those pressures are super low, and to my knowledge good injectors shouldn't leak down any? I dunno, maybe I'm overthinking

I'm gonna start with replacing the fuel pump and go from there. I believe with they injectors holding 41-42 PSI and the pump rated for 42PSI they aren't the problem. The margin of error here could be in the gauge or my lack of knowledge in doing a proper test. I mean I can barley squeeze the hose the gauge is attached to and change the reading. I'll redo the test once I get the correct pump installed.