Sniper issues

[JKIII FJ40]

Good afternoon, hoping someone may have run in to a similar situation as I am having now.

I have a 74 F.5, RobbMC power surge, sniper and recently installed evap system. I installed the EFI several months ago and have been running it on the weekends for up to an hour at a time without an issue. After sitting in the garage for about 6 weeks (knuckle rebuild/disc brake install) I finally got to drive it around and after afew minutes at highway speeds it starved for fuel. I struggled to get it home and primed the surge tank to get it running for a half of a mile at a time. Once the truck cools down it will restart like normal. Initially I thought it was fuel tank pressure that was causing the issue, I just installed the evap system and vented gas cap. It seemed to run like normal, but after 20 min the fuel pressure dropped and it was done. I have a good power source, I have fuel going in and out of the prefilter, fuel from the mechanical pump to surge tank, but no pressure at the sniper. Could it be the surge tank pump is failing after running for a while? The tank isn’t hot at all, I dont believe i have a hot fuel issue as I can put my hands on the tank and lines and they arent even warm. When running I have fuel pressure on the return line. I ran a hot lead to the tanks and I can hear the pump run. I believe the whole fuel circuit is operational.
Wondering what I am missing. Could the pump stop working after a while, could it be the fuel regulator, could it be something in the ECU or something totally else.

 

[Skreddy]

So is the power surge dry or close to it when this happens? If so, from my understanding how they work, this would be an issue with the engine mounted mechanical pump? Or a restriction in the supply somewhere to the PS.

 

[JKIII FJ40]

Hard to say, I have tried adding fuel and other times once cool it will restart. I have had this set up for a while and ran it without an issue until now. The mechanical pump hasnt had an issue keeping up before.

 

[mrboatman]

My guess would be your PS fuel pump is failing or the pump motor may have a internal thermal protection that is opening and shutting down. I do know 20 psi that is on your gauge will not run the sniper. At least my engine would not start at 20 psi, I was out of gas !!!

 

[Skreddy]

My guess would be your PS fuel pump is failing or the pump motor may have a internal thermal protection that is opening and shutting down. I do know 20 psi that is on your gauge will not run the sniper. At least my engine would not start at 20 psi, I was out of gas !!!

I saw the 20 psi as well but was hoping that was just a residual pressure reading after shutdown?
The mechanical pump failing was my first thought if the PS isn’t getting enough fuel. Keeping up at lower loads/shorter bursts but just not keeping up for longer demand.

 

[JKIII FJ40]

I installed a new pump last summer, hopefully thats not the issue. I un-hooked the feed line from the mechanical pump and have fuel when it cranks. I also have fuel flowing through the pre-filter too. I just ran across this article and clip , Builds - Project R2D2 Sixty - 1986 Retro Refresh - https://forum.ih8mud.com/threads/project-r2d2-sixty-1986-retro-refresh.1190200/page-12 for the same issue. wondering if the surge pump is failing or something else.

 

[Skreddy]

Looks like the issue with his was an obstructed return line?
Is that 20 psi on the gauge when running then?

 

[mrboatman]

So are you thinking a return line issue? That might be something to check.

 

[JKIII FJ40]

20psi after it shut off. only does it after its warm or after higher RPMs. Wouldnt return line cause it to build pressure instead of low pressure?

 

[mrboatman]

Only after it's warm or after high rpm's I would think of different issues. After high rpm's I would think the manual pump is not keeping up. After it's warm makes me think of the pump in the PS. Maybe the manual pump is failing and you are noticing it after your truck is warmed up and the rpm's pick up. I don't run the PS tank just the inline electric pump so just trying to think thru the possibility of issues.

 

[JKIII FJ40]

Nolan replied on another thread, he said his issue was the return line. This would explain why the PS was starved for fuel. Makes sense, I think.

 

[mrboatman]

Does your return go back to the PS tank or the fuel tank?

 

[JKIII FJ40]

sniper to PS, PS to tank, using the side return port on the tank

 

[JKIII FJ40]

so, issue of vaporizing fuel solved (thanks Nolan for pointing me in a direction). I had a plethora of issues, small pinholes in the exhaust, leaking intake/exhaust gaskets and header heat affecting fuel delivery. I repaired the exhaust leaks, new intake/exhaust gasket, moved the power surge, ran new lines and insulated them and now its running. Issues resolved.....well sorta. Now I am running really warm in the engine bay, like i dont remember ever being so hot. Engine is 194-196 like always and now the MAT sensor is way above the normal 89-92 degrees. Its over a hundred and at about 110 (got up to 120) it wont idle up. Had to shut it down for a while and nurse it back in the garage.
Outside temp was about 88-90. I did some searching and all i can deduce is a bad MAT sensor.....face plant. Any one had a similar issue? I will call Holley tomorrow.

 

[merbesfield]

Pardon my ignorance, but is this EFI conversion different than others? I don’t remember seeing the cylindrical alum thing in other builds. The issues you are having make me wonder if all EFI conversions are this complicated. I thought EFI was supposed to lessen the problems.

 

[JKIII FJ40]

in most cases they are quite simple and bullet proof. Up to this point, my issues were external factors that affected the sniper. Now that i made all the changes that affected the sniper I have one more problem different from the others.

 

[merbesfield]

in most cases they are quite simple and bullet proof. Up to this point, my issues were external factors that affected the sniper. Now that i made all the changes that affected the sniper I have one more problem different from the others.

What is the reason for adding the RobbMC PS?

 

[zerotreedelta]

At least for those with a tank with the factory fuel return line, it's definitely not needed. I think some of older (pre-74?) rigs may not have a factory return line, so the surge tank can help there vs pulling the main tank to add that fitting. At least on my '76, the return line is there, and it's much simpler (and cleaner under the hood) to not have that...as well as less moving parts, as the mechanical pump gets removed.

More typical use cases for that setup are buffering for high HP, but the F/2F definitely isn't that.

 

[JKIII FJ40]

I installed the surge tank under the hood versus a frame mounted pump. My main reason for installing the EFI was trouble free service, based on users' issues including my own i was 75/25 on adding it. I'm sure it would work in the end; the surge tank allows me to unhook and remove the sniper and go back to a carburetor in an hour or two.

 

[JKIII FJ40]

my 74 had a return line on the tank and hard pipe. After some pipe bending it wasn't that big deal to add a hard-line return and plumb into the tank. and in the event i decide to pull the sniper i can add a carburetor with a return line.