OK, so that clears up the question if Dave is French...
Stumble/Hesitation AND stalling: *solved, fuel pump*
- Thread starter Bill 1960
- Start date
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Not precisely vapor lock, however I have experienced gas boiling in the fuel rail on a Jeep 4.0. Not driving, though. Jeeps will do it under specific circumstances when parked and then restarted hot, say 5 minutes later in hot weather.
The heat from the exhaust manifold boils the gas in the rail, and when you start it, it will have a dead miss for a few seconds until the vapor is cleared. Jeep issued a revised insulator to try and fix it IIRC.
Insofar as today’s patient, the only theory I can invent where both problems spring from a single cause is if the pump is somehow having a suction side leak and injecting air into the fuel system. Which seems unlikely with a submerged pump. I will have them save me the old one for dissection.
The stumble does seem to increase in frequency as I’ve drawn down the fuel level to make it easier for the tank removal.
The heat from the exhaust manifold boils the gas in the rail, and when you start it, it will have a dead miss for a few seconds until the vapor is cleared. Jeep issued a revised insulator to try and fix it IIRC.
Insofar as today’s patient, the only theory I can invent where both problems spring from a single cause is if the pump is somehow having a suction side leak and injecting air into the fuel system. Which seems unlikely with a submerged pump. I will have them save me the old one for dissection.
The stumble does seem to increase in frequency as I’ve drawn down the fuel level to make it easier for the tank removal.
Well, at least that observation reinforces the theory that the pump is having issues.
Curious - where have you been off wheeling?
I also forgot to mention that during the stalling episode ( problem 2) my initial thought was overheating of something because it ran a short while after each brief rest. During the more extended cool down, I hosed the FPCM down with brake cleaner to chill it. After which it’s never stalled again. Which is one reason my eye is on the FPCM, I suspect it may be the heat sensitive component.
Back in the days when I serviced industrial electronics, it was not unusual to have a component work fine at room temperature but fail at elevated temperatures.
Back in the days when I serviced industrial electronics, it was not unusual to have a component work fine at room temperature but fail at elevated temperatures.
We’ve been working our way across the country, started in NC and now in MT. I think the stumble may have begun in MO, but I had a brake booster start leaking vacuum there and I attributed the idle issue to that.
Got to WY before the booster got changed and I realized there was something else going on. Then a few days later the stalling issue. No wheeling since then, she has to stay in reach of a tow truck until I get this sorted.
Our plan is to drift NW until the change of color begins and then drift back SE through UT and CO and back to FL for the winter.
For the long interstate hauls she’s towed behind the motorhome.
I believe the pressure is regulated by the ECM and FPCM telling to pump when it needs to be on or off. A haywire FPCM (or pressure sensor) could definitely cause pressure fallouts (along of course, with a pump that can’t respond to the commanded state).
How far NW?
Maybe eastern Oregon, if we can find accommodations there. It’s a tough year, post lockdowns everyone wants to be outdoors and everything is full to capacity.
In past years we have been free agents, able to land a spot in just about any area. Not this year- finding a vacancy is determining what area we land in.
The reason I ask, is if you can get there, Crater Lake is something you are going to want to go see. It is spectacular. Mount St. Helens is also cool but not as cool as Crater lake.
When I move back to Mo. next year, I will miss my yearly trips to Crater Lake.
When I move back to Mo. next year, I will miss my yearly trips to Crater Lake.
Light at the end of the tunnel? New Delphi pump went in today. Truck has not missed a beat since. The idle miss had become more frequent as I was running the fuel low to prep for the tank removal.
So maybe one bad part WAS the source of both issues? But I’m at a loss to explain how it could be showing good pressure AND causing a miss. I’m going to dissect the old pump and see if there’s any evidence to be seen.
I will still be replacing plugs, wires, and the FPCM. No more breakdowns in remote places wanted!
So maybe one bad part WAS the source of both issues? But I’m at a loss to explain how it could be showing good pressure AND causing a miss. I’m going to dissect the old pump and see if there’s any evidence to be seen.
I will still be replacing plugs, wires, and the FPCM. No more breakdowns in remote places wanted!
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