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]

  On 5/28/2019 at 2:55 PM, Hudy said:

Fuel injectors have been replaced.

 

Crankshaft position sensor replaced.

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With what?

[Hudy]

  On 5/28/2019 at 3:30 PM, Jeep Driver said:

With what?

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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]

  On 5/28/2019 at 3:41 PM, Jeep Driver said:

What's keeping you from installing a new pump?

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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]

  On 5/28/2019 at 4:15 PM, Pete M said:

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

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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]

  On 5/28/2019 at 10:08 PM, 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.

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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]

  On 5/29/2019 at 9:08 PM, 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.

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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]

  On 5/29/2019 at 10:10 PM, 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.

 

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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]

  On 5/29/2019 at 9:08 PM, 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. 

 

 

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  On 5/29/2019 at 9:25 PM, Pete M said:

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

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Do you want to rephrase that question? LOL

 

[Jeep Driver]

  On 5/29/2019 at 10:57 PM, Hudy said:

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

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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]

  On 5/29/2019 at 11:32 PM, 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.

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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]

  On 5/30/2019 at 12:00 AM, Hudy said:

 

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

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

[Hudy]

  On 5/30/2019 at 1:04 PM, 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?

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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 4:16 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.

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Anxious to hear about any updates, bro.

 

 

[Hudy]

  On 6/5/2019 at 3:43 PM, coolwind57 said:

Anxious to hear about any updates, bro.

 

 

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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.