No start after a long drive on a very hot day...worn IP?

[Big Red Suburban]

The suburban usually fires up with a second or two of hitting the starter, however after long trips on very hot and humid days (>95 degrees, > 80 humidity) when it is shut off and sits for a while (like 20 minutes or more), it won't start. It just turns over like normal but no fire. It may take 4 tries of the starter for 5-8 seconds each before it finally starts to fire and takes off. I don't think the problem is glow plug or glow plug controller related.

My theory is after a long trip on a hot day and it is parked, the heat from the motor heats up the fuel in the IP and fuel lines above the motor. Since hot fuel is thinner, the IP can't get it to a high enough pressure to pop the injectors and thus a no start condition. BTW, the IP has almost 70,000 miles on it (replaced once at 120,000 miles) and I've upgraded to high flow injectors which demands more out of the pump.

This has only happened a hand full of times, and I have since just made a point of not shutting it off on long trips when it is really hot.

I have tried to restart it immediately after turning it off when hot and it fires right up. So it is definately related to sitting for a while while heat soaking everything under the hood.

Any ideas? I previously installed a remote mounted (under front bumper) FSD and cooler so I doubt it is the culprit.

[Hubert]

Have you checked your lift pump recently?

Mine was bad and it took a little more cranking than normal if it had sat for a while then ran fine. It had normal power no stalling sputters etc. It just took a few extra cranks for the IP to suck in some fuel.

Could be that and the heat soak builds pressure in fuel lines bleeds back pressure off then cooler it has to pull fuel up to it again (or sucks some air then has to purge air)???.

On edit: Could be a sticky fuel shutoff solenoid. If it long cranks tap it lightly while someone cranks it. Easier said than done.

Who knows about FSD's mine started dying with the long cranks. It did this periodically before any shutdowns or stalls. Might want to get a cheap backup just in case.

But if not try to give more information for more ideas.

If its hot and you cut it off and let it sit has a long cranking episode then starts can you cut it off immediately and restart easily or does it long crank again?

I would not think ~ 95F was all that hot. The filter bowl does have a heater in it someone want to say what the IP wants the fuel temp to be???

If the IP can't meter fuel precisely it will shutter and buck at low fuel demand and changing load. Like on easy launch with a manual transmission.

Any increase in smoke or decrease in performance?

[Big Red Suburban]

I've checked the lift pump, still has right at 4 psi (which is what it had when I installed it new about 20,000 miles ago). It also has a new fuel filter and I run additive in every tank.

There has been no increase in smoke, performance is still the same.

The next time it has a long start episode I will shut it back off and immediately try to start it again. If it fires right up it would support the hot fuel, if it takes a long time again, it would lean me to believe something else is still really hot and causing the problems.

[Barry Nave]

BRS
Is fuel tank full?
After hot shut down try opening the fuel cap and notice how much vaccum is in the tank.

[Big Red Suburban]

On this last occasion, the fuel tank was between 1/2 and 3/4 full. I have noticed that when I stop for fuel and open the tank, there is quite a bit of vacuum in the tank. It's done this as long as I can remember...what does this indicate?

[Hubert]

Should not be vaccum. There may be positive pressure thats ok. The diesel cap has a one way checkvalve. Maybe if you have too much vaccum the LP doesn't work well at first.

I don't if this is real smart but I cleaned mine then sucked through it and blew from tank side. It should act kind of like a plugged exhaust on scuba regulator. You can suck but not blow through it.

The pressure comes from the warm diesel circulating back to the tank and heating the air in the tank.

[GMC Hauler]

What model injection pump do you have?

[Big Red Suburban]

I'll have to figure out if it was sucking air in or blowin it out. I assumed it was a vacuum.

IP is model 5288.

[tom.mcinerney]

Red--
JD [GMCTD] has posted some figures and description of proper tank cap ops, maybe try 'search'. The caps are known to occassionally fail.

Hubert-
The heaters warm to 80* F or so. A fuel injection ace once suggested that warmed fuel is easier to pump, less wear on FIP.