97 Dynasty looses fuel prime?

[Greg Carter]

Our 97 Dynasty sometimes seems to loose its prime and have to use the electric Wynn purge system to get it re primed and running.

it only does it after it sits for some time. Could be 2-3 days could be weeks .

i just changed out both fuel filters as well as new O rings in the Wynn filter system but it still happens.

not sure if there is a check valve built into the engine driven lift pump but was think I’d get a new one soon anyways.

8.3 Cummins with the Mechnical injection pump.

thought someone might have an idea.

cheers

[Jim Bob]

My 95 did this for a while and I eventually found a crack in the fuel line.  Luckily it was in an easy spot to splice in a piece.  It didn't leak fuel at all, just would suck in some air and I just stumbled upon it one day.  Engine ran fine once primed so it took me a fairly long time to figure it out.  I tried making sure the filters were tight, etc. with no joy.  Pretty much my only solution for a while was a stick I kept in the front that I could use to reach through the grill and hit the Wynn button.  Hope this helps.

 

Jim

[veraken]

Had a similar problem on mine.  Replaced the fuel shutoff solenoid and solved the problem.  If you go this route, check the bolt spacing before ordering.

https://www.ebay.com/itm/271834521395

[BlueSteele]

I had a similar situation. I replaced the lift pump and things got better, but it happened occasionally. I found a bad clamp on the fuel line and replaced it. That seems to have solved the problem.

[Greg Carter]

Thanks for these replies and ideas.

i did change the fuel shutoff a little while ago but not related to this issue 

jim bob you mention a cracked line so I’m wondering if you recall where that was and what type of line. 

And Blue Steel since you said a clamp do you recall where that was.

we had the return line hose split a couple years ago close to the injection pump return outlet so it was a easy fix sine there was enough hose to cut out the split. That hose is the only connection that I’m aware of that used a hose clamp.

time to open up the tank side panels I guess and start a detailed trace. Funny thing is like Jim Bob I’ve found no fuel leaks anywhere at this point. 

When that return line split it spewed fuel all out the back and over the toad so easy to spot that one.

thanks again. Lots of great info and help here.

 

[RoadTripper2084]

13 hours ago, Greg Carter said:

new O rings in the Wynn filter system

Not to derail the thread, but would you happen to have the specs on the o-rings required for the Wynn system?  I'd like to pick up a set of spares for mine "just-in-case".

Thx.

[Greg Carter]

I wouldn’t call that a derailment at all. I found this information about the Wynn system some time ago just don’t recall where it came from but happy to pass it on.

hope it helps.

cheers

 

 

[Jim Bob]

8 hours ago, Greg Carter said:

Thanks for these replies and ideas.

i did change the fuel shutoff a little while ago but not related to this issue 

jim bob you mention a cracked line so I’m wondering if you recall where that was and what type of line. 

And Blue Steel since you said a clamp do you recall where that was.

we had the return line hose split a couple years ago close to the injection pump return outlet so it was a easy fix sine there was enough hose to cut out the split. That hose is the only connection that I’m aware of that used a hose clamp.

time to open up the tank side panels I guess and start a detailed trace. Funny thing is like Jim Bob I’ve found no fuel leaks anywhere at this point. 

When that return line split it spewed fuel all out the back and over the toad so easy to spot that one.

thanks again. Lots of great info and help here.

 

It was after the Wynn system and up close to the engine... see the picture with the smaller rubber tube and 3 clamps on it.  It has been a couple of years so my memory is not great, but I had worked on the fuel shut-off in the past and was just reaching in there to check it and noticed the rubber line was looking old and cracked.  Once I touched it and moved it a little it did leak fuel, but had not done that until I messed with it.

[Greg Carter]

Jim Bob thank you so much for getting that picture. 

Clearly now to me that’s the same return line that we had split a few years back so it’s highly probable that it’s cracked again further down like yours did. It does surprise me however that it would cause the issue without leaking. 

On my 95 I have to change a check valve on the steel part of that line at the banjo fitting.

the diesel injection shop that sold me the replacement said that they need around 15-20 lbs before they open and then the fuel gets returned to the tank. So much that one doesn’t know but I guess I should check that valve on our 97 as if it’s stuck open and that line is cracked or split then I guess that air could make its way back to the injection pump but now I’m just guessing. 

Still not hard or very expensive parts 

once again many thanks

 

[Jim Bob]

you are very welcome.  I think it was a very slow progression...  sometimes would take a month to lose prime, then just gradually got shorter to where I'd have to prime it almost every time.  Was never really an issue as I'd just hit the button and it would start right up afterwards.  And again, I was lucky to be reaching around in there and I guess I finally broke it completely open because it did start leaking at that point.  Hope you figure it out, can be a real challenge to track down the gremlins sometimes.