Yet another air intrusion problem? I think..

[olBlue]

Hi everyone so here the back story, 94 idiT fully rebuild engine 3 years ago.New everything- short block ,heads, R&D inj pump, injectors. Facet lift pump with 7psi regulator in engine bay. I deleted fuel filter setup and relocated to frame with. Engine always started up and ran great.this last summer I redid the frame and I replaced the rear most tank and lines to the frame. Since then over the summer its been getting harder and harder to start. Now I'm scared to drive anywhere and leave it sit for 20-30min without having to crank it forever at half throttle for it to start. and once it does a mile or so it surges like i hit the nitrous button and then returns to normal the rest of the trip.

So now this winter I'm looking into it. Keep in mind truck has probably 1000miles on it since rebuild. I see the drivers rear injector return cap is wet around the base. So once again I buy a whole new return kit from Pensacola Diesel. Replaced everything with brown Viton o rings and lots of rubber grease. Also installed check valve in 2 ft line from Lift pump to Injector pump.Cranked a ton of times and started engine and let idle to operating temp. No problems.
Let truck sit overnight.. same thing. wts light comes on, glow plug controller clicks once, wts light goes out and i crank and crank until it fires up then dies, crank some more, half throttle, fires up and runs perfectly. shut it off and 4 hrs later starts right up no problems. What could I possibly be missing??

Tonight I ran it to operating temp, shut off and clamped off the return line at the back of the engine to see if i can eliminate the line to the tank. I did notice my fuel pressure gauge on the lift pump slowly drops but stops if i pinch the lift pump to injector pump line.Is this a issue? Im at a loss right now. I got some clear hose and will try installing it on the lift pump feed and return line next I guess. Any help is greatly appreciated. I basically want to run this truck into a lake.

 

[homelessduck]

A big issue with return kits is the cheaper quality ones often times have small burrs that damage the o-ring as they are pressed on. I'm pretty sure Pensacola is in the "Hall Of Shame" . @typ4 's kit ( russrepair.com ) would have been a better choice.

 

[Scotty4]

I was having the same starting issue. Put a check valve prior to the mech pump and have no issues now. Maybe you have a leak in your modified supply lines somewhere: filter, pump, etc.

 

[olBlue]

I might have to try one of his kits. And I do have a check valve between the electric lift pump and injector pump. I just think it’s weird if I have the return clamped off and the lift pump supply clamped off, the regulator pressure drops to zero in a hour. But I don’t think this is anything because it’ll start right back up. It’s the sitting overnight that’s the problem

 

[miles1400]

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[olBlue]

You think it’s a lift pump problem?pump seems like it’s doing it’s job

 

[Philip1]

Many people have issues with the faucet pumps. The pump itself tends to struggle to supply enough fuel and the screen bowl on the bottom of the pump has frequent issues with air intrusion.

 

[olBlue]

What pump would you recommend? If I clamp off the faucet on the inlet and outlet it holds pressure over night until i unclamp it so I figure id rule that out

 

[olBlue]

I had the feed line before the injector pump and the return line clamped overnight. Tonight I Just removed them and it read 4psi on the lift pump. I let the wts light shut off and cranked it for 5 seconds. Nothing. Fully cycled the key and throttled halfway and it fired right up. So if this is normal for 42deg garage temp I may have a return line issue to a tank

 

[Philip1]

What pump would you recommend? If I clamp off the faucet on the inlet and outlet it holds pressure over night until i unclamp it so I figure id rule that out

I personally am running a holley black fuel pump but I need the extra flow for my larger ip. The holley red is good for stock because it has plenty of flow while not needing an external regulator. The next step up is the holley blue which does need an external regulator then holley black that needs a regulator as well. The largest disadvantage for the holley pumps is they are noisy but they do get drowned out by the engine.

 

[olBlue]

I wouldn’t be worried about the noise. Definitely will be considering that pump. The only thing that I wonder about is I keep reading a electric pump will band aid a return line air intrusion problem. If that’s the case then none of my return system should matter right? The truck should still fire up after wts light goes out

 

[IDIBRONCO]

I think that it's a Band Aid for fuel drain back problems. A return line air leak is on the other side of the fuel system. They commonly occur together, but not always. I believe that air intrusion is usually only an issue on the feed side. It's from air being sucked into your fuel system before the IP and injectors. A return line leak can cause hard starting problems, but it shouldn't affect the running of an engine like air intrusion will since it's at low pressure and it's after the injectors.

 

[Farmer Rock]

I agree with @IDIBRONCO . The electric pump will only mask drain back problems, but won't mask return line issues. I would definetly be looking at the return lines first.



Rock

 

[olBlue]

I removed my pressure regulator and installed a clear hose from the lift pump to the injector pump keeping the check valve I added in place. It actually started up a lot faster this time and once running no air bubbles are seen. Do you guys think a facet (unregulated) can cause my timing to advance? It has been this way since I installed it and i timed the engine this way too and wonder when regulated to 6psi if it was throwing off timing. I was going to check my timing this week. just have been busy.Just a thought. thanks guys for all the help!

 

[Jl elevatorman]

If the Facet pump is electrical, put a diode ( 15-20 amp), in the Glow Plug circuit. Connect this to the feed wire for the pump. This will prime the injector pump on startup. Problem Solved.