Lift pump delay
 

First of all, I would like to say hello to everyone on this forum. I am not new to diesels just to the forum. Okay, I recently purchased a 99 24 valve from a buddy. The truck has a new injector pump with less than 5k. The truck has a problem with the lift pump delaying before attempting to run at all before starting the truck. If you do not wait aprox. 10 sec, until you can hear some lift pump noise, the truck does not want to start. If you will wait until the lift pump runs tho, it starts fine. My first though was to replace the lift pump, I did that. No luck. I have another 99 that is wrecked, so I decided to change the ecm on the engine. No luck. Change the truck ecm, still no luck. Any ideas? Is the anything else that the truck uses when cranking to tell the lift pump to run such as maybe crank sensor, etc? When the key is initially turned on, there is no noise at all , then about 10 seconds later, you can hear a little lift pump chatter the you can start. Any help would be greatly appreciated!

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The lift pump will only run for a second when the key is turned on, and will not run until the key has returned from the start position to the run position. You can make it run for about 20 seconds if you bump the starter, and leave the key in the run position. If you can't start without making the lift pump run, I would say you have fuel leaking back.

when the key is initially turned on, the lift pump never says a word, then maybe 10 seconds later, as soon as noise is heard from the lift pump, it starts fine. I replaced a vp 44 today on an 01 and installed a new lift pump on it. Trying to determine the cause of my problems on my 99 , I decided to kill the power to the lift pump on it then try to start it, it will not start either with lift pump no power. You plug lift pump back in, it starts immediately no problems, no delays either.

That sounds very odd to me! :s: Maybe try bumping the starter and see how the lift pump reacts to that.

When I bump the starter, a couple times, it will usually go ahead and make lift pump cycle, then starts fine. If I try to just start the truck immediately it turns over about 10-15 times then starts, about the equivalent time it takes if you turn the key on then wait out the delay. Stumps me.

Pressure Regulating valve perhaps? It may not be holding enough fuel in the VP to make it start.

Replaced overflow valve today as well. I did some testing on this truck as well as another 99 model that starts fine. I checked lift pump pressures on both trucks and when the lift pump would stop running on both trucks, pressure would fall back to zero. Evidently these pumps don't retain pressure? I don't understand. The only thing that I have determined was both this truck and the 01 model had to have the lift pump active to start.

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okay, did some more checking, actually what i've noticed is the wait to start light is also delayed. If you wait until it finally cycles, all is well. I searched the forums and found no other threads relating to this. I did google it and there were threads and same problems on other forums but no one ever showed any solutions. Any ideas?

There is a small passage in the overflow valve, so fuel pressure can escape all the time. Mine doesn't hold pressure either when the pump is off.

As for the second part, that sure is weird. To clarify, you turn the key on and the WTS doesn't illuminate right away, but will later?

If the WTS light is coming on and then the lift pump starts after the light goes off then the lift pump might not be getting enough voltage to operate correctly. Mine is slow or weak sounding when the WTS light is on but as soon as the light goes off it picks up alot. Also if it is very cold there the the heater may need to cycle in order for the truck to crank. I tried to start mine the other day w/o cycling the heater when it was 10 outside and it had to spin over alot more than normal to start and when it did it cutoff. If it is cold outside and the heater is cylcing before you start it then this is probably normal.

Yes, you turn the key on and the wts is delayed before it illuminates the instant it illuminates, you can hear lift pump noise and it will start fine.

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Temp is about 70 deg. here today.