1998.5 24V It starts fine and quick, runs strong then the fuel pressure will fluctuate and it stalls. It will not restart.  I found the fuel overflow valve is getting stuck in the full open.  Replaced the fuel overflow valve but it keeps happening. If I push the ball on the overflow valve it will start again.    

What is you fuel pressure?

14 psi at start up/idle an around 10 during normal driving.  But when this happens the fuel pressure will start fluctuating then drop to zero and it happens when minute or less.   

Should be around 7-8psi when cranking and 17-20 running. Your wts light comes on every time you start ? Any codes? 

Lift pump bad and starving the motor? Next time when it shuts down just bump the starter, no engine start, and see if the pump is running. It should runfor 20 seconds or so. If it is then open the filer drain and see if any fuel is coming out.

17 minutes ago, dripley said:

Lift pump bad and starving the motor? Next time when it shuts down just bump the starter, no engine start, and see if the pump is running. It should runfor 20 seconds or so. If it is then open the filer drain and see if any fuel is coming out.

 

He'll need to key off for 10 seconds. Then do the starter bump. Then it will run the 20 seconds. The stall will be counted and key bump will not function. The ECM has to be down for 10 seconds and do a fresh reboot for starter bump to work.

 

Watch the fuel pressure. 

He is right about that.

How are you pushing the "overflow valve ball"?

 

 

The only way to touch the ball in the overflow valve shown, would be to remove it completely.  The "ball" you may see in the end of it is just a plug. (it could be a screw or another type of plug)  If pushing it makes a difference something is really weirdly wrong.

 

If that valve being open drops your pressure enough that the engine stalls, you have other problems. Behind that valve is a VERY small hole the flow through which is much less that the injection pumps use of fuel during running.  

 

If you are losing pressure during running, this valve not working properly, I highly doubt is the problem.  You are either experiencing a failing pump,  you are sucking air into the pump, or your fuel filter (or in tank sock) cannot flow enough to maintain pressure.   Speaking of that, where do you pick up your pressure?  can you check pressure before the fuel filter?

 

GL  HTH

Hag

Edited February 3, 20205 yr by Haggar

Overflow valve...

 

Overflow valve removed. Testing of the overflow valve is inside the article above. 

 I had to have it towed home the first time it then just happen to push the small ball on the end of the overflow valve and it started right up. I did change the overflow valve just in case and it did it again and push the ball at the end & it started right up. I did test the valve using the process Morpar1973man & it did work.  I haven't driven it from that point. 

 

I'm measuring the pressure at the filter on top & today it was ~15 psi at idle.

The first time it happen I did see the fuel pressure start fluctuating just before it died.

 

I'll see if I can measure the pressure before the filter.  

How to you check for air leaks in the fuel system?

I also need to see if I have an codes-

 

I did have the VP44 & fuel pump changed ~ a year ago

I used my cheap OBD II code reader , Maxiscan Ms 300 and it indicated no codes

http://www.maxi-scan.com/38-autel-maxiscan-ms300-MS028.html

On 2/2/2020 at 5:39 PM, Mopar1973Man said:

He'll need to key off for 10 seconds. Then do the starter bump. Then it will run the 20 seconds. The stall will be counted and key bump will not function. The ECM has to be down for 10 seconds and do a fresh reboot for starter bump to work.

 

Mine will take another bump to run the pump immediately after the pump shuts off. No need to turn the key off. Unless I misunderstood.

Edited February 4, 20205 yr by kzimmer

Steve,

The ball on the end of the overflow is a plug.  pushing it is like kicking the front tire.  The fact that it started after would have nothing to do with that plug.  Now is it saying that you grounding the VP did something?  (I am sure you were leaning on the fender to reach in) You pushing on the VP did something?  Did you disturb some wiring to reach it?  Not certain.   Don't stay focused on the plug in the overflow.  Start looking at the other things that happen when you go to push this plug....   See if one of the other things you are doing while going to push this is what is helping it run.

 

GL

 

Hag

Edited February 4, 20205 yr by Haggar

Thanks Hagger-  I'll start those checks & thanks for the advice.  I'll start rechecking the grounds & connections. Most likely have to wait for it stop working again to diagnose which is frustrating.  

1 hour ago, kzimmer said:

 

Mine will take another bump to run the pump immediately after the pump shuts off. No need to turn the key off. Unless I misunderstood.

Mine will do that if you have just bumped for priming or whatever. You can do it many times with out shutting it off. 

 

But if the engine shuts down for any reason other than turning key off it wont do the prime without turning the key off and starting over.

 

Hope that makes sense.

The first time it died,  it was low on diesel not near empty. So, I went and got fuel & tried to start with no success.  

Thanks for the advice and info.  

 

 

Edited February 5, 20205 yr by JAG1

2 hours ago, dripley said:

Mine will do that if you have just bumped for priming or whatever. You can do it many times with out shutting it off. 

 

But if the engine shuts down for any reason other than turning key off it wont do the prime without turning the key off and starting over.

 

Hope that makes sense.

 

Yep, I understand now. Thank you.

20 hours ago, Scuba64 said:

The first time it happen I did see the fuel pressure start fluctuating just before it died.

It could be air leak in the suction side of the pump. He mentions that the fuel pressure gets unstable then it stalls. I've seen a truck with a bad pick up tube in the tank and would do something similar and start bouncing fuel pressure and then die. The fuel gauge still shows 3/8 of a tank and the tank had fuel but the stock pick up tube was cracked and get low enough it would suck air and quit. 

 

I would look towards filling the tank and trying again. Also after filling the tank and it stands for a period of time look at all the external plumbing on the frame rail and up for moisture or possible outward leaks. Suction side plumbing typically will not leak outwards but constantly sucking air inwards even parked. This makes it difficult but not impossible to find. 

 

On a partial tank use a shop vacuum and reverse it to the blow. Using the hose you can pressurize the fuel tank. This will help in finding any external leaks possibly.

 

Fuel pressure should not bounce or change a bunch while driving. 

 

 

35 minutes ago, Mopar1973Man said:

 

 

Fuel pressure should not bounce or change a bunch while driving. 

 

 

I would say yes, he does have a fuel supply problem like dirt clogged fuel basket screens or cracked draw straw. He might still have the in tank lift pump and be trying to suck fuel thru that . I'd be inside the tank to look things over and have a new 1/2 inch draw straw and big line kit and pre lift pump filter ready to install. You know my raptor lift pumps on both trucks had a little screen inserted in the inlet side of the pumps. Came that way new and had to be removed and add a prefilter to protect the lift pump.

Thanks Mopar1973Man & Jag1.  I'll try your recommendation.  I did notice that when first starting it up the pressure will fluctuate 2psi until it warms up ~ 5 minutes. s that normal?  

 

 

No it is not normal. Fuel pressure low like that typically a bad pump or possibly air leaking in. Air bubbles are compressible and will make the pressure lower. You could add a loop of clear tubing to look for air bubbles or foamy fuel.

Sorry the pressure was ~12 psi but would fluctuate 2 psi (10-12 psi up & down) for about 5 minutes.  Then stay at 12 psi.  

I'll try the clear tube this weekend & search for air leaks..