New VP44 - Engine requires excessive cranking when hot

[01cummins4ever]

9 minutes ago, dripley said:

Mine has always been key on about 1/2 second bump, bump the starter, no engine start, about a 25 second lift pump run.

You are correct, it’s the bump of the starter not the click of the key as I stated.

[pepsi71ocean]

1 hour ago, 01cummins4ever said:

IIRC the ecm is programmed on first click of key to give a 1 sec. burst of fuel, 2nd click 1 sec, and 3rd click about 10 to 15 sec. At least that’s the way mine worked when I had an electric pump.

 

 

It depends also on what flash was done. Dodge was flashing the ECM at one point to get rid of the bump cycles. 

[dieseled]

You might want to try an other relay , could be sticking closed

I had a bosch mini that kept running sometimes a few seconds after I turned my truck off

[Leaky88]

Thanks for inputs.  Also, the W-T Mod was done some months ago, followed Mikes lead verbatim. Noise is at acceptable normal level but I’m still pulling ALT fuse/connector to do a 2nd test WRT TC issue.  

 

Thats what I like about these trucks, you can always move on to another problem when in a state of consternation over another one. 

[Mopar1973Man]

7 to 12 PSI during cranking is fine. Above 12 PSI and hard starts happen. What happens the ECM attempt to advance timing too quick so the lift pump pressure is reduced by cycling the power at 50% duty cycle so the pressure fall and the VP44 can advance timing till the RPM's come up. 

 

[Leaky88]

3 hours ago, Mopar1973Man said:

7 to 12 PSI during cranking is fine. Above 12 PSI and hard starts happen. What happens the ECM attempt to advance timing too quick so the lift pump pressure is reduced by cycling the power at 50% duty cycle so the pressure fall and the VP44 can advance timing till the RPM's come up. 

 

Thanks. Explains why truck barely turned and fired using my Spare DDP-02 with less pressure.  So once started, is the 20 psi still OK for the VP44? (I might still be paying off the FASS 150. )

 

[dripley]

I have run 19 to 20 psi for the past 8 years. Nothing wrong with 18 psi either.

[Mopar1973Man]

17 to 18 PSI running here no issues. Cranks at about 10 to 12 PSI no starting issues. Fuel temp typically about 120*F with the summer heat.

 

Edited July 12, 2019 by Mopar1973Man

[Leaky88]

On 7/10/2019 at 5:02 PM, Mopar1973Man said:

7 to 12 PSI during cranking is fine. Above 12 PSI and hard starts happen. What happens the ECM attempt to advance timing too quick so the lift pump pressure is reduced by cycling the power at 50% duty cycle so the pressure fall and the VP44 can advance timing till the RPM's come up. 

 

Almost a year ago, I replaced my VP44, purchased through DAP. 

Truck runs fine, but I STILL have a HARD START issue when truck is hot. (I.e. I stop at a Rest Area on a trip.)

For the life of me, I cannot remember if the "failed" VP 44 had an issue with Hot Starts.  It could very well have been an

existing issue prior to my replacing the VP44 and I attributed the hard start problem to the old VP44. 

Regardless, the problem is still alive and well. 

Please note, the engine kicks right off with a mere bump when it's cold, regardless of time of the year. 

I have a FASS 150 aftermarket pump which produces a solid 18 PSI. (As has been pointed out, I realize a 95 would probably have been a better choice, but it is what it is.}  The cooling of VP44 was my primary concern when selecting the 150 over the 95. 

@dripley stated his truck starts every time HOT with 18 PSI, but I have read that some VP44's can be more sensitive to LP pressure than others. 

I did the HOT START relay mod, whereby I use a spring loaded switch in CAB to power a relay, that cuts power to FASS 150 during HOT cranking. 

It does nothing to decrease Starter Time on this HOT Start issue. 

There are no codes since I replaced the VP44 and truck runs fine aside from HOT Start issue. 

I'm ready to try something new. Since I really only need a Minimum of 15psi going down the road, the overflow opens at 14psi, and extreme pressure does nothing but heat up the fuel, I am entertaining cutting the FP back. 

 

 

Since the FASS 150 FP is non-adjustable, I understand I can trim the Spring on the FASS 150.  

Question: How much of the SPRING do I trim each time to "incrementally" reach the desired PSI. ?

 

 

 

Edited July 27, 2020 by Leaky88
edited because I inadvertently submitted before I was done.

[dripley]

7 hours ago, Leaky88 said:

@dripley stated his truck starts every time HOT with 18 PSI,

If I stated that l was mistaken at the time. My pressure is reduced during cranking in the 12 and less psi range. Kind of hard to tell since it cranks do fast. If mislead you or anyone else my apolagies.

Though mine did hard start this morning cold. I was sitting nose up on low fuel tank, might have got the return line out of the fuel, dont know. Had to hold the the key on for 3 seconds or so. I filled up and shall see what happens in the am.

[Mopar1973Man]

7 to 12 PSI like Dripley said is the optimal fuel pressure for starting. Above 12 PSI it tends to push the timing piston too far advanced making nearly impossible to start. Hence why the ECM pulses a 50% duty cycle during starting to reduce fuel pressure and make it easier starting. Way too many people are trying to keep above 20 PSI for run pressure and find out your starting pressure is too high. You could do the starter relay mod so during the time the starter is running it holds the power off to the lift pump. But I suggest just getting your fuel pressure down. You not going to gain any better return flow on the VP44 when the return hole is tiny any ways. Pull the overflow valve out and using a mirror and look at it. It's small port. 

[Leaky88]

Mike et al,,

 

I have also tried the Starter Mod with no joy.  I then went to the Relay Mod.

Question: What if I installed a Natural Gas 1/2" Ball Valve on the return side of the FASS? 

Looking at it, I could easily put 1/2" Push-on fittings on the valve.

Do you think this would work? 

Thanks. 

Leaky 

[CUMMINSDIESELPWR]

as long as you are above 15psi at any given time or throttle, you are fine. its the flow to open the overflow banjo that keeps the vp cool. 14 and below there is no flow.

[Mopar1973Man]

Just try and hold in the 14 to 20 PSI range optimally.

[Leaky88]

With the Fuel Pump Relay removed, it cranks a healthy 15psi of FP on the installed Mechanical Pillar Gauge.

I know the FP needs to be no more than 12PSI or I have Hot Start issues.  I got it.

 

Question remains: Would my idea of a Ball Valve on Return Side of FASS 150 allow me to control it?

Good/Bad Idea?

Has anyone done it?

I know the Air Dogs have an adjustment with lock nut on them.  But my FASS 150 does not.

 

Thanks.

 

 

 

 

[Mopar1973Man]

1 hour ago, Leaky88 said:

With the Fuel Pump Relay removed, it cranks a healthy 15psi of FP on the installed Mechanical Pillar Gauge.

Too high need to drop below 12 PSI. 7 to 12 PSI is a good cranking pressure. 

 

1 hour ago, Leaky88 said:

Question remains: Would my idea of a Ball Valve on Return Side of FASS 150 allow me to control it?

Bad idea it only going to make the pressure higher. Need to change the spring for a 14 PSI spring then shim to meet your pressure you want. You need more return flow. Mine is set for 17 PSI and typically only drops to 15 PSI WOT and then 7 to 9 PSI cranking.

[dripley]

1 hour ago, Leaky88 said:

With the Fuel Pump Relay removed, it cranks a healthy 15psi of FP on the installed Mechanical Pillar Gauge.

I know the FP needs to be no more than 12PSI or I have Hot Start issues.  I got it.

 

Question remains: Would my idea of a Ball Valve on Return Side of FASS 150 allow me to control it?

Good/Bad Idea?

Has anyone done it?

I know the Air Dogs have an adjustment with lock nut on them.  But my FASS 150 does not.

 

Thanks.

 

 

 

 

I dont think I have heard of anyone trying it that. It could work I guess. What effect it would have on pump I dont know. That in essence would do the same thing as the spring but outside pump. If you put it in and it does not work you just a little time and money but at least you tried. Just be sure the ball valve is safe with fuel and wont disolve anything into the fuel.

You know many years back I had low pressure issue with my in tank pump. No adjutments on that pump. So I added another pump on the frame rail and ran that for 4 years or more and it worked. This was pre forums for me. Dodge just wanted to sell me another pump. I wanted a solution. Nothing ventured nothing gained I guess.

[01cummins4ever]

5 hours ago, Leaky88 said:

 

 

Question remains: Would my idea of a Ball Valve on Return Side of FASS 150 allow me to control it?

Good/Bad Idea?

 

 

Thanks.

 

 

 

 

What are you trying to accomplish with this? It seems that if you try and cut off the return flow you are just going to create excessive pressure, Not quite sure if your issue is pressure related or not

 

After long hard starts does truck spit and sputter until it clears up, or does it idle and run normal even after a long hard start?

 

A few different scenarios  could be playing out here but leaning toward a heat soaked psg on the vp or possibly a slow and wore out starter not allowing good compression, I’m not sure if the tach will even register during cranking, I know mine doesn’t register until it fires off but it would be hard to notice being it usually fires in the first second or so. Just something to look into being its been known to solve others long hard start issues 

 

 

[Mopar1973Man]

Shouldn't be any valve on the return line. Truthfully should be no valves at all in the fuel supply system. 

[Leaky88]

OK.

No Valves it is. I've erased the idea. Sorry I brought it up. Bad Bad Bad idea.  I'm down with that.

I'm just tired of the HOT START issue.  Any engine that needs to be cranked excessively before it fires, most especially a  Diesel,

is embarrassing and I'm certain the Starter does not enjoy it either. 

The "load-tested" batteries are good, the Starter is strong, and has no issues.

 

Now back to the back to the Ball and Spring at the RETURN on the FASS 150.

Did not find a 14psi Spring at Vulcan, contacted them asking for one, and apparently they don't stock 14 PSI Springs.

Is there another source?

 

Thanks.