Well, there went $150 and an evening.

So the truck has lately decided to be slow to start/long crank times. So I did some research and figured I'd check the fuel pump pressure and it didn't pass, so I replaced it with the recommended Delphi unit. Hoped I solved the problem.

Last two days, same issue.

When I get in, first thing in the morning, it will occasionally take 5-7 seconds to start. When it does, it chugs and has a very rough idle. I can apply gas, and it will even out just fine... until it let off the gas. Then we are back to chugging. It will run like this with barely enough power to pull itself for 3-5 minutes, when it finally starts acting right.

It does not always do this. It is almost always first thing in the morning, but not every morning. I get no codes. Copper plugs, wires, cap and rotor, NGK O2 sensors all replaced in the last 10k miles. Plenum done with aluminum plate in the last 5k miles, IAC and throttle body cleaned at that time. Oil pressure is fine (40-50, no smoke, and gets between 9 and 11 MPGs. When it runs right, it has plenty of power (for a 2wd 5.2 with the original tranny).

One last thing. When it does this long crank, once it starts if I let it idle for 30 seconds and then shut it off, it will start again right away and run right. Full power, no chug.

When I did the plenum, I replaced the timing chain with a cloyes double roller and used the "Advance 4*" setting. Could this be the culprit? Everything else is stock...


Give me some ideas guys! What am I looking at? What part do the Mopar gods demand of me?

 

If it was a mechanical issue, it would do it every time. (cam timing)

How old are your wires? Good quality? Is your issue weather dependent? (worse when humid/raining?)

Fuel pressure coming up good at first start up?

 

I figured its electrical somewhere, but wasn't sure if the advanced timing was confusing the PCM from time to time.

Wires were replaced with the plugs, cap and rotor about 10k miles ago. Store box brand, 7mm. They're routed according to the TSB.

Haven't noticed any direct weather correlation, although it has been raining the last few days.

Haven't retested fuel pressure (have to rent the fuel pressure tester from OReillys again), but I'm assuming so. When it starts right, it's perfect. I replaced the fuel pump last week and it started perfect 8 mornings in a row. Better than before, without any key dance. But Thursday and Friday I had problems.

 

Try doing the key dance again when cold. See if it starts right up.

 

So, you're thinking fuel pump still... Ugh. Worst news I've heard all day.

 

you could be loosing pressure at the opposite end... at the fuel rail, injectors, lines. the service manual has the procedure to test the fuel pressure at all ends to pin point where you are losing the pressure. doubt you had a bad pump and replaced it with a defective one, though not impossible. i would check your lines for kinks injectors and rail.

 

Okay, so i rented another fuel pressure tester from Oreillys today.

Now, I havent driven the truck since Friday. When I put the tester on, i read 0 PSI. Nothing. Great.

Turn key to "On", and pressure jumps to 25 PSI.

Turn to start, get the typical rough start, but pressure jumps to 48 PSI steady.

Turn off, drops down to 40 PSI.

Turn back to start, starts just fine and pressure jumps to 48 PSI.

Turn off again, drops down to 40 PSI.


So that's all wonderful news.

I decide to check a few other things while I have the tools out:

Injector resistance all checks out between 12.3 and 12.5 ohms, just like they should.

I remove all the spark plugs, and see some discrepancies. Remember, all plugs have less than 10k miles on them:





Does #3 look a little more worn/burnt than the other 7? If #3 is bleeding down, wouldn't I see it on the plug?

I also checked my compression, and even though I only had time for a dry test, those numbers did not look as good as I hoped. (Motor has 126k miles)

Dry test:
#1: 130
#3: 125
#5: 140
#7: 125

#2: 150
#4: 135
#6: 130
#8: 120

Lowest is 120, so that's good, but there's too much variance between it and the highest at 150. Since those are both on opposite sides of the same bank, i'm a little concerned.

Now, I haven't noticed any other problems usually. With a good start, there's plenty of power and I'm not losing any coolant or oil, so I wouldnt suspect a head problem.

Anyone have any suggestions for me at this point?

 

Looks like something is up with that whole bank of spark plugs.

Did you gap them when you installed them?

Did you reset your pcm after changing all these sensors and pumps? Sometimes it fixes weird things.

Not sure the pressure is supposed to drop to 0 psi. Isn't the check valve in the pump supposed to keep it about 40ish? Not sure on this info. I could be way off.

 

Ham, I was thinking the same thing. Regulator should keep the pressure around 40, even after a couple of days.

Yes, I did gap all the plugs, and I reset the PCM. Besides, the long crank is a recent development since I did the plugs, O2 sensors, plenum, etc.

I looked around for any obvious signs of leaking fuel... but there's nothing. No apparent damage to the fuel lines or rails, no smell of raw gas, etc.

I think the discoloration on 1 &7 is just shadow. In person, only 3 looked bad, maybe a little bit on 5.

If an injector ring was leaking, what would I see?

If an injector was bleeding into the chamber overnight (not shutting completely), what would I see?

Really hoping for a simpler fix here than replacing the fuel pump again. That'll suck.

 

I think the fuel pump is probably fine. It should build more pressure at initial prime, but..... since it sat for a few days, not a really big surprise.

What I AM seeing though, is the passenger side is running lean. Drivers side looks good. (yes, even number three is acceptable.) Think I would have a look at the fuel rail, and see if the crossover tube isn't damaged/kinked/plugged/restricted in some fashion.

Do a wet test (compression) as well.