New DAP VP44 - Hard Start When Hot?

[Octafish]

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?

 

 

 

 

 

 

 

 

 

[Mopar1973Man]

20 minutes ago, Octafish said:

Starting pressure with my Fuel Boss is 20 lbs.

 

Too high starting pressure needs to be 12 PSI down to 7 PSI.

 

 

[Dieselfuture]

1 minute ago, Mopar1973Man said:

 

Too high starting pressure needs to be 12 PSI down to 7 PSI.

 

 

Lots of people with mechanical pumps and they don't have a hard start problem because of high pressure. I can see if it takes longer to start how mechanical pump will increase pressure which does not help the situation. If electrical pump was wired to a battery and had constant pressure on start up I'd say it may be the problem. But if everything is working as it should and truck fires up half the crank, then pressure won't be at 20 yet.

My opinion is if you didn't have this problem before you changed vp then it's more likely what it is. 

[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 cranking to reduce fuel pressure.

 

Like pull the belt and test. If it starts hot then it's too high of cranking pressure. Like us electric guys just unplug. If it's still a problem there is a delay relay that could hold the power off during cranking. This is not an option on mechanical pumps.

[Octafish]

I've been running the DDRP alone with the Fuel Boss on the sideline with the belt and fuel lines disconnected for test purposes.

I'll disconnect the power to the DDRP when I get home, motor hot, and try starting it after a few minutes.

Maybe that will tell me something.

 

With my old VP (before it crapped out), the Fuel Boss never caused a problem with 20 lbs pressure at start up.

 

 

[Dieselfuture]

21 minutes ago, Octafish said:

With my old VP (before it crapped out), the Fuel Boss never caused a problem with 20 lbs pressure at start up.

Does pressure go up to 20 in one second or ? 

If you disconnect your fuel pumps, not sure if fuel can be pulled through a positive displacement pump (mechanical) 

Vp will start and idle without auxiliary pump if fuel is not restricted. 

[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 boss until it fires up then you can see 16 or more instantly. 
 

I would personally disconnect the ddrp, it’s not needed at start up, that would eliminate the high 20 psi, during cranking.

 

I agree the VP is not liking the high pressure but that also could be a VP problem but reducing the pressure might help the issue. Years ago when I changed my Vp I had a long hard start like 20 seconds when it was hot, pouring cold water on the electronics and it would fire right off. I ended up exchanging it for another one. 

[Mopar1973Man]

Old video...

 

It will show first attempt a ari bubble comes through on the second it shows the 50% duty rate of fuel pressure bouncing. 

 

[IBMobile]

I have the fuse for the electric pump pulled and use only the Full Boss when starting/running.  I have only used the electric pump to prime the fuel system when replacing the VP44 and again when the injectors were replaced. 

[wil440]

9 hours ago, 01cummins4ever said:

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 boss until it fires up then you can see 16 or more instantly. 
 

I would personally disconnect the ddrp, it’s not needed at start up, that would eliminate the high 20 psi, during cranking.

 

I agree the VP is not liking the high pressure but that also could be a VP problem but reducing the pressure might help the issue. Years ago when I changed my Vp I had a long hard start like 20 seconds when it was hot, pouring cold water on the electronics and it would fire right off. I ended up exchanging it for another one. 

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 garden hose

[Octafish]

Update:

 

I'm back to working on the hot start issue after being preoccupied with stuff.

Went back thru the Blue Chip diagnostics.

 

Cold start - starts in a split second.

Hot start - spin, spin, finally starts.

 

Fuel Boss with low pressure at startup but builds to 20 quickly - same results. 

 

So I got out the garden hose and cooled down the VP after I got the motor hot.

It started instantly.

To make sure the wasn't a fluke I repeated the process later that day.

Same results. Hot starts quickly with the garden hose.

 

I contacted DAP about warranty on the 2 month old pump.

I did get the one with new electronics.

They looked up the order, said it sounded like a warranty issue and told me to call Blue Chip.

Said that they would help with warranty quicker than DAP.    OK???

 

So I call Blue Chip. Very helpful people but they ask why I called them?

The person I spoke with said he hadn't heard of Diesel Auto Power. 

 

So I call DAP back. Got a different person.

They said their warranty people will call Monday.

We'll see how this goes.

Edited May 2, 2020 by Octafish

[dripley]

Maybe @dieselautopower's rep thought you bought it from Blue Chip if you mentioned their name with the testing you did. 

[Octafish]

I thought about that but in the same conversation they looked up my order and account to confirm my purchase and date.

Not a big deal on sending me to Blue Chip. It was great jawing with them.

I just thought it was odd.

[dieselautopower]

That is odd.  Funny... Friday was insanely busy. Mitch said he got the RMA request in for you.  Thank you for your patience.

[Mopar1973Man]

Personally, I say the cranking pressure is too high. Pull the belt on the hot start I bet it starts fine.

Edited May 5, 2020 by Mopar1973Man

[Octafish]

1 hour ago, dieselautopower said:

That is odd.  Funny... Friday was insanely busy. Mitch said he got the RMA request in for you.  Thank you for your patience.

Not a problem at all on Blue Chip.

That was strange but I probably should have just kept that to my self now that I think about it.

I apologize if that came across as a negative.

 

DAP has always been great to work with.

They have always taken care of any problems quickly and professionally.

I'll always go there first.

 

[wil440]

1 hour ago, Mopar1973Man said:

Personally, I say the cranking pressure is too high. Pull the belt on the hot start I bet it starts fine.

  my gauge does not move at all until it's running then it comes up like the altimeter on a Saturn V

 

On 5/2/2020 at 12:53 AM, Octafish said:

Fuel Boss with low pressure at startup but builds to 20 quickly - same results. 

 

So I got out the garden hose and cooled down the VP after I got the motor hot.

It started instantly.

To make sure the wasn't a fluke I repeated the process later that day.

Same results. Hot starts quickly with the garden hose.

?? surely this cannot be a problem with the Fuel Boss,  it apparently worked fine before, Fuel Boss, Assassin... etc, cause no start  up problems for anyone

[Octafish]

1 hour ago, Mopar1973Man said:

Personally, I say the cranking pressure is too high. Pull the belt on the hot start I bet it starts fine.

Mike, with the Fuel Boss I don't believe you get full pressure until the motor actually starts.

So I felt kinda safe assuming that.

However, I did try disconnecting the belt and had the same hot start problem.

 

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.

 

 

 

[Mopar1973Man]

 

1 hour ago, Octafish said:

However, I did try disconnecting the belt and had the same hot start problem.

So the pump is having issues...

 

1 hour ago, Octafish said:

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

Something is seized up like timing piston hence its working after cooldown with water. 

[Dieselfuture]

7 hours ago, Mopar1973Man said:

 

So the pump is having issues...

 

Something is seized up like timing piston hence its working after cooldown with water. 

It's either piston or more than likely psg solder problem, at least that's what I found researching over years.

Ether way vp needs changing