5.0 Slow to start.... sometimes

[RomeovilleIL]

Was looking at the wrong engine. SOHC parts galore, 5.0 not so much.

 

[MINERALGSVT]

Well, that didn't last too long. It worked great for a few days, now it's back to what it used to be... I can't guarantee that the part I swapped in was good, but it sure did work nice for a few days.... I don't get it..

 

[RomeovilleIL]

The pressure damper from what I was reading is supposed to basically even out the pulsing pressure from the pump. In theory if it the diaphram was broken or leaking you could have an issue with surging or bogging, but your truck runs fine once started right?

Some thoughts: Even though the previous owner said a new pump was put in with the new tank, you have no way of knowing what brand or model was actually used, if in fact they were replaced. I suspect there may be something going on either with the pump or the filter sock. I think at this point the best thing to do would be stick a fuel pressure gauge on the system and watch the starting pressure and check leak down. It's possible having the rail open and all pressure relieved for a while helped the pump hold pressure when restarted, especially if its a little weak. Also possible there is something in the tank, sock, or line that is blocking the flow until it is moved with enough gas. I did find a piece of plastic (might have been from a shipping cap, not sure though) in a filter sock once causing hard starts. Personally I would drop the tank and visually inspect rather than guess.

 

[MINERALGSVT]

The pressure damper from what I was reading is supposed to basically even out the pulsing pressure from the pump. In theory if it the diaphram was broken or leaking you could have an issue with surging or bogging, but your truck runs fine once started right?

Some thoughts: Even though the previous owner said a new pump was put in with the new tank, you have no way of knowing what brand or model was actually used, if in fact they were replaced. I suspect there may be something going on either with the pump or the filter sock. I think at this point the best thing to do would be stick a fuel pressure gauge on the system and watch the starting pressure and check leak down. It's possible having the rail open and all pressure relieved for a while helped the pump hold pressure when restarted, especially if its a little weak. Also possible there is something in the tank, sock, or line that is blocking the flow until it is moved with enough gas. I did find a piece of plastic (might have been from a shipping cap, not sure though) in a filter sock once causing hard starts. Personally I would drop the tank and visually inspect rather than guess.

Yeah, truck runs great once it's started. You make some good points and things that have crossed my mind. I find it hard to believe that 2 different dampers would give me basically identical issues.

I'm going to check fuel pressure and go from there - should be able to tap into the schrader valve on the rail, right?

 

[RomeovilleIL]

Yeah pressure check is the valve under the hood. I'm pretty sure you can get a pressure gauge kit as a rental. Pressure should come up to mid-60's with key turn priming and then hold for an hour or more with slow or little pressure loss. I know the trucks can run on 35+ pounds of pressure so often a weak pump will still operate, but are hard to start at lower levels. BTW a lot of different pumps will fit and run but are the wrong flow rate. There is every possibility someone put in a new pump that is for the older return type system and only puts out 40-45 pounds of pressure rather than the 65 returnless requires.

 

[MINERALGSVT]

Ok, so I did a little more digging... Joe Dirt described my exact symptoms in an issue that he had a couple years ago...

His fix was a crankshaft position sensor...

anyway - I plan to check the fuel pressure and see what it says

 

[MINERALGSVT]

Ok, digging this one back up.. I recently replaced the water pump so while I was there, I swapped the Crank Position Sensor since Joe Dirt had the exact problem.... no joy.. I never got around to checking fuel pressure.. I couldn't round up the right size adapter and then life just got in the way...

I did talk with a tuner that I plan to use to put a tune on the truck and he suspected it might be a leaky injector.

Recap...

- truck starts fine after sitting all night or some period greater than 4 hours
- truck starts fine after sitting 5 - 10 minutes
- truck is slow to start from somewhere around 30 minutes to 4 hours or so
- outside temp doesn't seem to affect
- no check engine light
- truck runs great

Thanks

 

[CDW6212R]

Hi Todd, have you ever first turned the key to on without starting it, and then turn it off and back on again? That builds more pressure, if the first priming wasn't enough do to nothing in the rails beforehand. My old 93 required 2-3 primes of the pump when it had set for a long time, the injectors or the FPR leaked down too fast. That one was fine when warm, short trips.

I'd have also suggested to check the CPS, even just resetting the timing with the tool might have been it. You've done that now, so check the fuel pressure next. It should jump right up to 55-62psi each time you turn the key on, and running is supposed to be the same. My 99 had a very slight leak in the fuel pump rubber hose, which hurt the pressure at higher rpm's.