Competition Engine quit after hard run!

[MD500E]

I got into it for about 5 seconds and then had to lift off quickly because of an up coming turn. As I entered the turn I realized the engine had quit. I thought, here we go again, It was the same situation as 2 years ago when my vp-44 died just after tapping the pump wire. I cranked it on and off for about 5 min and got nothing. The only thing that gave me hope was seeing another 24 valve truck stall after a dyno run because it some how got air in the lines. After some more cranking it eventually started and acted as if it too had air in the fuel system. Does any body know what happened, and how to avoid it in the future, aside from not letting off too quickly?

thanks



Kevin

 

[jwilliams3]

Air charge in the fuel system, causing a stall is a great possiblity.

I have seen it happen twice w/twin setups (I helped get the trucks started again).

I would advise carrying a can of ether with you, to help with these situations.





Besides this, I think you have answered alot of your own questions in your post.



--Justin

 

[Cooker]

Being an undervalved guy I am not too affluent when it comes the 24v but I have also heard of this happening. From what I understand it is more common with twin setups.

 

[offshoreracr]

Originally posted by MD500E

and how to avoid it in the future, aside from not letting off too quickly?

thanks



You answered your own question, aside from that carry a 19mm-3/4 wrench and bleed an injector or two, that will get it running fairly quick.

 

[JTroiano]

Be carefull with ether and the grid heaters. I just let the clutch out before it stops rolling and it starts back up. The first time I didn't know what happened and took the whole truck a part.

 

[FreeBMW]

There was a truck on the dyno today & it did the same thing after each pull.







It had a FASS system..... I see you have one too, wonder if that might be part of it... . had to crank it for a while to get her going again..... it was like it was starving fuel.

 

[Big P]

Fuel supply isn't the problem. There was a post about this exact same thing reciently. The vp44 is pretty much pumping all the fuel it can while you abruptly lift off the go pedal it basicly pushes out all of its' fuel before it can refill itself under idle conditions. Like what has been said before just try to lift slowly. If it does stall the easiest way to restart is to crack the injector lines to re-prime.

 

[FreeBMW]

Good to know..... It will be helpful next time we have a high HP VP44 powered truck on the rollers.



Thanks!

 

[mgoncalves]

This isn't limited to the "Big" powered trucks.



Mine has done it with three's and a comp. It didn't totally stall, but was very close and luckily worked it's way out with a little revving.

 

[MD500E]

Thanks for the replys, it is nice to know I am not alone with this issue. I guess I will have to start carrying a wrench just in case!

 

[Huff N Puff]

I'm running into the same problem.

I did notice that after it stalled,I heard my fuel pump,which is controlled by the ECM, buzz in areally strange manner,after it stalled. After waiting a while I cranked it,and the pump buzzed normally. My theory is the ECM may be pulsing my fuel pump relay,causing the VP44 to suck air. I'm going to try a different relay control. I'll let you know what happens. Merv

 

[Lsfarm]

Same Experience

I've had the same experience with the ECM giving an erratic or pulsed signal to the lift pump circuit.



What is confusing is that this was on a truck with twins, and the stalling only occured when the truck was pushed past a rather mild 35psi. The fuel pressure at the inlet to the VP44 was at least 8psi.



If the pedal was let off rapidly, the truck would stall, and when a restart was attempted, then I could hear the lift and pusher pumps pulsing instead of running steady. I jumpered the circuit and cranked untill I got it to restart.



I installed a toggle switch into the circuit to provide continous current for the lift pumps. But I haven't yet gone out and flogged the truck again to see if I could get it to stall.



What is the reason for a pulsed ECM signal?? And why does this occur only when the truck has been run with higher than 35psi boost?? The truck had been flogged very hard prior to the twins with NO stalling problems?? What does the boost pressure have to do with the ECM lift pump circuit??



And here is what really bothers me: two of the above mentioned trucks have a FASS fuel system which is supposed to provide all the fuel needed, and the fuel is NOT supposed to have entrained air, so WHERE is the air coming from that is 'vapor locking' the VP44??? I had hoped that adding a FASS to this truck would cure the stalling, but now I fear that it is must more money spent in a futile pursuit of reliability.



I'm begining to really dislike these VP44's, even though the one on my truck has performed flawlessly so far.



Merv, plesse let me know what you find out.



Greg L. The Noise Nazi.

 

[JTroiano]

I don't think it is fuel supply. I think it is eather the fuel cavitating in the high pressure lines or there is to much cylinder pressure when you let off the go pedal and it pushes air back into the lines. Twins usually make more pressure. It never happened to my truck with a single turbo, but the first time out with the twins it did it. Hope this helps.



Jon T

 

[Lsfarm]

reversing pressure

Thanks Jon I too was thinking that the cylinder pressure was the only difference between running a single and twins.



I guess that with twins the turbos can still put out some boost for a longer time when the pedal is lifted compared to a single . Apparently the VP puts out enough pressure to open the injector even at idle throttle position and then the cylinder pressure is high enough to push air back into the injectors and lines and maybe even to the VP44 causing vapor lock in the pump.



If the above scenario is right, then just hesitating a second or two when backing out of the throttle before lifting all the way out of the throttle should do the trick. Just long enough for both of the turbos to spool down and not put out any residual boost.



Does this make sense to you??



I'll have to road test this technique tomorrow.



Greg L The Noise Nazi

 

[JTroiano]

Lsfarm, I was thinking of a dash pot like on an old carb. It will hesitated the throttle closing all by itself. I forget all the time and let of to quick and it stalls. I'm usually rolling and I just let the clutch out and it starts back up. I've heard that if you can get it to crank quick enough it will start without cracking the injector lines.



Jon T

 

[mgoncalves]

The one time my truck threw it's fit was with a sharp let off at 42 psi with the single charger. That doesn't seem like enough pressure to cause this. But then again, it didn't totally die, it just got super rough like if I had a couple of injector lines loose, then cleared up.



Matt

 

[JHerrlich]

I had the same thing happen to me, I bought a new lift pump and replaced it just in case that was the problem.

 

[Big_Daddy_T]

Mine used to do it fairly often after a hard run. With Super mentals and a drag comp. Only a few times did I have to bleed the air out. Usually it would start back up after 15 sec crank time. I kept a 19mm wrench under my seat.

 

[csevers]

This is an interesting thread I to have had truck die on a pulling truck once and it took a lot of cranking to get it running. Does anybody get any codes set when this happens?? I have not, chech engine light has never even flashed when it happened.

A few things to think about: the vp uses fuel pressure to make timing changes , the ecm regulates voltage to the liftpump circuit at different times, injection pressure is what? 19k? what are cylinder pressures? I don't have the anwsers but just thinking.



Craig

 

[Big P]

I think Jon T is right. I think maybe it's a "timing overlap". You lift off the pedal under high boost creating high cylinder pressure, but you lifted so fast that the vp-44 tries to inject fuel under idle condition cylinder pressure. For a split second the injection pump isn't pumping fuel at a high enough pressure to overcome the the cylinder pressure so the air actually blows back into the injection lines. If this is true I wonder it a BD B. O. V. would solve the problem?