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New DAP VP44 - Hard Start When Hot?

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Installed a new VP44 from DAP.

Truck starts lightning quick as it should when cold.

 

I can let the truck sit for 5 days, nose uphill, starts in about half a revolution as it always has.

So no siphon or fuel leaks.

 

However when the motor's warm, not so much.

Takes 3-5 seconds but does start every time .

But let it set for several hours, cooler engine, no problem.

 

Starting pressure with my Fuel Boss is 20 lbs.

Out of curiosity, I put my DDRP back on which also runs around 20 lbs starting pressure.

Same hot start problem with either.

Is 20 lbs too much?

 

 

No codes with a good scanner.

Wait  to start light normal.

 

Didn't have this particular problem before the old pump died.

 

I'm leaning towards a faulty new VP.

Any suggestions?

 

 

 

 

 

 

 

 

 

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  • wil440
    wil440

    Bang on... my Assasin is zero at startup, I have no electric pump, as soon as it starts its at 14psi at idle to just over 22 max. Never needed a priming pump as it will suck a football down a gar

  • Mopar1973Man
    Mopar1973Man

    Above 15 PSI mine won't start either. That's why cranking pressure is dropped is because too much pressure will cause over advanced timing.   This is why ECM duty cycles the power during cra

  • 01cummins4ever
    01cummins4ever

    Your fuel boss alone will only deliver pressure according to your rpm at cranking which should be around 250-300 rpm if I remember right. And at that you will only be creating around 5-7 psi with fuel

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11 hours ago, Octafish said:

3 times now, I've tried the garden hose cool down trick and the truck starts immediately.

The last thing I want to do is pull the pump and I feel like I've tried everything.

Plus I never had a hot start problem with the old pump.

Sounds like the pump to me.

I had the same issue with my 2001 24v, instant start up when cold but long cranks when hot. It turned out to be a bad overflow valve. I replaced it and it doesn't skip a beat. 

17 minutes ago, Royal Squire said:

@Cronus577 Just curious, did yours start if you poured cold water over pump?

I never tried. It started happening out of the blue with no trouble codes so all I could think of is either the VP went bad with no symptoms or the overflow was sticking when it was hot. 

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