Trouble Starting When Hot

[Hudy]

I’m on a 5 year journey of hammering down my rough start problem. I’ve searched high and low and can’t find this exact problem here already. 

 

The symptom:

Cold start = Starts fine

Warm/Hot Start = Have to “cycle” three times. By this I mean running the starter for ~3-5 seconds, stopping, and doing it again. It’s three times, every time, for the last 5 years. 

 

Priming the pump (click to “on” a few times) has no effect. I have to actually run the starter. 

 

Fuel injectors have been replaced.

 

Crankshaft position sensor replaced.

 

I found a thread on NAXJA that mentions a fuel pump issue. The suggestion here was that the pump could malfunction in a way that when it’s hot it can’t prime correctly. To my knowledge this is the original pump at 240k. 

 

How should I diagnose this? Am I missing anything? 

 

 

[Jeep Driver]

35 minutes ago, Hudy said:

Fuel injectors have been replaced.

 

Crankshaft position sensor replaced.

With what?

[Hudy]

2 minutes ago, Jeep Driver said:

With what?

Volvo Injectors.

Sensor is from NAPA.

 

This problem existed before and after both replacements.

[Jeep Driver]

What's keeping you from installing a new pump?

[Hudy]

29 minutes ago, Jeep Driver said:

What's keeping you from installing a new pump?

 

To be honest, nothing. Curious if maybe I’m missing something before I dive into it. 

[Pete M]

that is... weird.    what's your fuel pressure during this no-start event?  do you have spark at that time?

[Hudy]

20 minutes ago, Pete M said:

that is... weird.    what's your fuel pressure during this no-start event?  do you have spark at that time?

 

I do not have a pressure gauge, but I guess it would be worthwhile to pick one up.

 

Good question on spark; I guess I could check this by pulling a wire, putting a plug on it, and grounding it? 

[Pete M]

I bought a simple whatchamacallit.  autozone might rent both for free.

 

 

[fiatslug87]

I had the same issue a while ago, I replaced the injectors with referb ones and it's been fine ever since.

I did replace the exhaust manifold and O2 sensor at the same time but I assume those were not the issue.

[Hudy]

1 hour ago, fiatslug87 said:

I had the same issue a while ago, I replaced the injectors with referb ones and it's been fine ever since.

I did replace the exhaust manifold and O2 sensor at the same time but I assume those were not the issue.

 

Just did some reading and this makes perfect sense. Picking up the loaner fuel pressure tester tonight and will do some testing tomorrow. Maybe I replaced my leaking injectors with leaking injectors 

[thehomelesdepot]

I have been having the same problem recently. Truck starts up fine, but if I try starting after I shut it off, it puts up a fight and keeps cranking. I suspect the fuel pump is starting to go, so its getting replaced this weekend and I will report back if that fixed the problem.

[Hudy]

Okay, fuel pressure gauge is connected.

 

Prime is 14psi then drops to 12psi.

Running at 8psi.

Shut it off it drops to 6psi, and it is at 0 at one minute and 30 seconds. 

 

 

[Pete M]

what's the pressure when it's having problems?

[Hudy]

A few interesting points:

 

1: I pulled the fuel rail and the injectors are not leaking, so that’s out (I think?)

 

2: My fuel pump wasn’t always priming. More often then not, I cycle the key and it stays at 0. If I attempt to start it jumps up.

 

3: Briefly during testing It was starting but then dying. I remembered there is a white resistor next to the airbox. Cleaned, and now it is priming every time. 

 

Is there a way to rule out the pressure regulator leaking down?

[Hudy]

And back with more...

 

The priming issue is still hit and miss. The hesitation to start occurs when there is no prime. 

 

I do have spark - thanks Pete - neat tool. 

[Ωhm]

58 minutes ago, Hudy said:

Prime is 14psi then drops to 12psi.

Running at 8psi.

Shut it off it drops to 6psi, and it is at 0 at one minute and 30 seconds.

 

Those are terrible number for fuel pump pressures. Should be as follows:

Prime 39psi

Running 31psi

System should hold 30psi after KEY OFF for at least 30 minuites or more.

 

[Hudy]

40 minutes ago, Ωhm said:

 

Those are terrible number for fuel pump pressures. Should be as follows:

Prime 39psi

Running 31psi

System should hold 30psi after KEY OFF for at least 30 minuites or more.

 

Holy cow. Wouldn’t I be having more issues with it this low? 

 

I guess I’m in the market for a new pump. 

[Jeep Driver]

2 hours ago, Hudy said:

Okay, fuel pressure gauge is connected.

 

Prime is 14psi then drops to 12psi.

Running at 8psi.

Shut it off it drops to 6psi, and it is at 0 at one minute and 30 seconds. 

 

 

 

2 hours ago, Pete M said:

what's the pressure when it's having problems?

Do you want to rephrase that question? LOL

 

[Jeep Driver]

33 minutes ago, Hudy said:

I guess I’m in the market for a new pump. 

Guys will tell you- "don't fix what's not broken". 

 

I'm in this camp-

 

You got 30 years and 240K out of the pump............it's been broken for a long time. 

 

Fix it before you're stranded.

[Hudy]

25 minutes ago, Jeep Driver said:

Guys will tell you- "don't fix what's not broken". 

 

I'm in this camp-

 

You got 30 years and 240K out of the pump............it's been broken for a long time. 

 

Fix it before you're stranded.

 

Yeah, agreed. New pump is ordered. I’ll shoot an update when it’s in. 

[coolwind57]

I've been plagued with this for some time.  I've pretty much covered every component with the exception of a new fuel pump.  

 

Slow to start when it's warm.  Fires right up after sitting for many hours and especially overnight.  

 

I get a plume of gas odor when it does finally fire up during those excessive warm crank times.  You?

[Pete M]

13 hours ago, Hudy said:

 

Yeah, agreed. New pump is ordered. I’ll shoot an update when it’s in. 

 

add in a new ground for the pump while you're under there.  

[Hudy]

3 hours ago, coolwind57 said:

I've been plagued with this for some time.  I've pretty much covered every component with the exception of a new fuel pump.  

 

Slow to start when it's warm.  Fires right up after sitting for many hours and especially overnight.  

 

I get a plume of gas odor when it does finally fire up during those excessive warm crank times.  You?

 

Yep, same gas plume here. Hoping to see the pump sometime next week. In the mean time I’ll be running the tank down. 

 

Good call on the ground suggestion, thanks Pete.

[coolwind57]

On 5/30/2019 at 12:16 PM, Hudy said:

 

Yep, same gas plume here. Hoping to see the pump sometime next week. In the mean time I’ll be running the tank down. 

 

Good call on the ground suggestion, thanks Pete.

Anxious to hear about any updates, bro.

 

 

[Hudy]

53 minutes ago, coolwind57 said:

Anxious to hear about any updates, bro.

 

 

 

Alright! New pump is in.

Priming at 39, running at 31. Holding pressure. 

 

Still not priming every time though. When it doesn’t prime it takes a little longer to start. Relay problem?

 

Ive had several hot starts and it’s starting in a reasonable amount of time. No gas plume. 

 

I did drop the tank and it took forever. I think it could reasonably be done in the truck. 

 

I used a carter pump. It was not a perfect fit and took some finagling to get it to work. The screen on the old pump was completely clogged. Photos attached.

 

I’ll post an update if anything changes. I do have to mention that the AZ pressure gauge I used initially no longer works, so perhaps my initial readings weren’t right.