Engine/Transmission (1998.5 - 2002) Intermittant start problem

[RandyCarter]

starts normal but on occasion will not start at all.

 

[JLandry]

Randy,

I think we're going to need a lot more information than that if we're going to be able to help you. Can you please elaborate a little?

Questions:

How long has this been happening?

How many miles on the truck?

What percentage of the time does the engine start and not-start?

When the engine does start, does it do so quickly and without any difficulties?

How does the engine run once it starts?

When it won't start, do you crank and crank and the engine just never fires?

Is the no-start condition random or have you been able to tie it in to any particular temperature or other circumstance?

Have you checked the fuel pressure?

When was the last time you replaced the fuel filter?

Was anything else done to the truck about the time this condition started?

Thanks,

John L.

 

[RandyCarter]

Thanks JL. Only for a month, 95000miles, 10% at first and becomming more often, starts normal when it does start, run normal (no power loss or surging), when it malfunctions it will not start (even with lots of cranking) until it sits for nearly an hour, fuel pressure is good (indicator light installed with pressure switch) fairly new filter and no water etc when drained. Also does not throw any codes. It acts like a sticky relay. Thanks again, RC

 

[JLandry]

It acts like a sticky relay.

RC,



The next time this happens, try swapping out the ASD relay with another relay in the PDC (the Power Distribution Center which is located on the driver's side fender under the hood) and see if that helps.



Low battery voltage to the ECM can also prevent the engine from starting, so you might also try jump starting at least once when this problem occurs just to rule that out.



Please keep us posted and we'll try to come up with more ideas.



John L.

 

[RandyCarter]

Thanks John L,
Now that it has not started several more times, the ASD relay has been swapped, and a jump start, not seaming to make any difference. I have tracked down the wire,(red with green stripe) according to the maintenance manual to supply power to the fuel pump (shut off solenoid, i suspect) and it does drop to about to about 11 volts during cranking. Applied battery voltage there but still no start. After letting sit for 1-2 hours then will start again, and runs fine. Never has quite while running.

 

[JLandry]

... it does drop to about to about 11 volts during cranking.

RC,



That should be adequate voltage.



I'm beginning to wonder if it's not a heat soak problem with either the ECM or the FPCM (Fuel Pump Control Module) on the VP44 fuel injection pump. Is this problem only occurring after the engine has been warmed up and shut down, or does it also happen when the engine is cold?



You might consider hot wiring the VP44 using THIS POST as a guide. When the VP44 is completely disconnected from the engine wiring harness and provided power, the engine should start and idle normally. During this test the accelerator pedal will not work and the ignition key will not shut of the engine. To kill the engine, simply pull the ground jumper wire off the VP44. During this test the MIL (check engine light) may illuminate and the stored DTC's (Diagnostic Trouble Codes) will need to be erased using your favorite code scanner.



If the engine still won't start with the VP44 hot wired, then you can safely assume it's malfunctioning and needs to be replaced. If the engine does start, then the problem will be elsewhere and we'll have to continue brainstorming.



Regards,



John L.

 

[RandyCarter]

Thanks John,
yes, seems to be related to heat sink. Always starts when cold, or after sitting for 1 + hours. and always runs good when running. I will try the hot wire to eliminate all other possibles and get back. Thanks much
Randy

 

[VHolloway]

relay going bad try starter relay clean both battery cables ends real good and + at starter. my 99 was doing the same thing it turned out the relay was going bad slowly.

 

[RandyCarter]

Thanks John,
Just to follow up a little. Hot wired the VP44 after not starting, and started OK. Changed the Cam position sensor, problem still existed then changed the crank position sensor and the problem is solved. Even a little better mileage. found a small crack in the plastic of the crank position sensor.

 

[JLandry]

Randy,



Thanks for the follow up post and congratulations in figuring it out!



John L.