Fuel pump experts: Help me diagnose this problem

I run an Enderle 990 fuel pump. Yesterday in testing right after I shifted into 2nd gear I heard a whooooosh and thought sure I had thrown a blower belt. Never heard anything like this before. My mind told me the rpms went up and I lost g-force. When I looked at the data though I never gained any rpm, no problem with driveshaft to engine rpm, etc. But then I noticed that right when I heard the whoosh, the logger shows my fuel pressure suddenly dropping to zero. There's about .15 seconds from the fuel pressure dropping until I lifted off the throttle and manually shut everything off.

So today I got to checking everything out. I pulled the pump of and spun it with a drill. Couldn't pump any fuel at all. Wouldn't draw. If I put the inlet side directly in a bucket of water it would pump, but when hooked to a fuel inlet line it wouldn't draw 4". I took the pump apart and there are no obvious broken parts. Turning the shaft turns everything appropriately, etc.

But I think for some reason it suddenly lost prime midway through a pass.

Who can help me out?

 

look and see if your pump has a sleve in it if it does it might have gotten turned and now blocking the fuel pick up..Dave

 

Let's assume the pump is ok for a moment.
Bad inlet hose,
collapsed inlet hose
inlet fittings on pump and tank need new o-rings (sucking air)
ran out of fuel or pulled a hole in the fuel volume/level
Since you didn't say you damaged the engine, funky sensor?

Dave Koehler
http://www.koehlerinjection.com

 

Dave, I think you've got my contact info. Give me a call if you can this morning. Fuel level was and is still about 80%. I think it's a -12 inlet line with a pancake filter between the pump and tank. The tank sits behind my seat so the entire line is maybe 18" long and there's no evidence of collapse or leaks. When I took the pump out as I lowered the intake line down to the fuel level the fuel flowed right out with no restriction. The lines themselves are new this season. In other words - I think I ruled out most of the easy answers. SO call me please.

Matt Harnish

 

Any chance something is going on with the vent? Is it a new tank?

Scott Hall
Sales Engineer
Moroso Performance
115ATAD

 

Scott,

It's a 2012 American Dragster with a plastic tank behind the driver's seat. I plumbed all of the returns back to a manifold on the inlet side of the pump. That left me three -8 fittings on top of the tank that are all being used as vents now (12"-18" of -an hose looped vertically once).

 

Mike - I have an over-center bracket with spring to hold the shut-off open. And I physically shut it off as soon as I heard the issue. I thought I hadn't tightened down the fuel pump and expected to see it had wiggled out. But no - it was in there nice and tight, fully engaged. So when I took out the pump I expected to see a broken shaft like you mentioned. But nope. It was fine. As was the coupler to the cam drive, which itself was fine and wouldn't spin freely when engaged - i.e. nothing physically broken.

I talked to Dave Koehler, and I do run my return lines into a manifold plumbed to the intake side of the fuel pump. I need to recheck all of those for tightness/seal because if I had a leak in one of those lines it would have sucked air. I'm overnighting the pump to Dave for inspection and/or rebuild as necessary. Meanwhile I'll keep testing other things on my end.

 

How about describing the way your pump is mounted and driven --- have you verified that it is still being driven properly by the cam spud or whatever it's mounted to ? Did the rest of your motor functions look good on your graph ?

What was your boost curve doing at the moment of woosh ?

Where are you picking up your fuel pressure reading at ?

 

Drive

The shaft might not be long enough and slip out of the drive spud .

 

In response to the prior post, I am reading fuel pressure after the pump but before the K-valve.

I need to recheck the shaft engagement, as perhaps it could have slipped out?

My data from the failed pass looks virtually identical to the prior pass until suddenly the fuel pressure crashed.

I went back to the shop last night thinking somehow somewhere I must have had a loose line or fitting that allowed air to be introduced to the system, breaking prime and causing pump cavitation. Honestly it would be easier if that's what I had found. Instead, every single hose to -AN connection and every -AN to -AN coupling pressure tested great. Couldn't find a single minimal leak in the system anywhere.

Dave Koehler gets my pump today. At this point I'm not sure if I hope the pump is good or hope the pump is bad. Thanks for everyone's thoughts so far.

 

A couple weeks ago I had a pump go bad real fast and it resulted in a broken blower belt, 3 melted pistons, bad head gasket, warped valves and heads that needed welding.

Years ago I broke a pump shaft and it didn't hurt the engine.

Last year I kept hurting an engine and main pill changes and nozzle jet changes did not change the tuneup, this ended up being a torn o-ring on the inlet of the pump that was allowing it to suck air.

So according to my experience if you had the above it would be obvious.

Did the engine restart later in the pit area?

 

Did not try to restart engine. Wanted to inspect for cause before trying to restart. Have subsequently turned it over with no issues. Plugs good, etc. Should have fuel pump back on Friday and will try then.

And I agree with you - I assume had I not lifted and shut off almost instantly that I would be facing a hefty repair bill.

 

Sounds like a venting problem

 

Fuel pump tested and checked out ok. Looks like I'm re-plumbing a bigger line from the tank to the pump and validating my vent size. Thanks for all the comments and help.

 

Another update. Fuel pump failed at track testing again Sunday. It now looks like the o-ring between the pump housing and the face plate may be bad, allowing the pump to suck air between those two mating surfaces - at least enough to break prime. New o-ring arrives today. If this is it, I'm surprised it hasn't happened to others over time.

By the way - I replumbed with -16 hose and have three vents. One -8 and two -6. Even with the cap off the tank, a 2 1/2" hole, the pump couldn't draw.

 

Good point. I pressure tested every single line. But that was in a disassembled state, which wouldn't have shown a stress crack in a fitting. Thanks for the suggestion. I'll check for hairline cracks.

 

JMatt --- if you tested your lines properly you would have seen a hairline crack in the tube fittings - how did you test them ?

I am also wondering how the pump performed on the flow bench but not on your car ?

I have to wonder what you are forgetting to post up ?

Something is missing here --Did the problem you originally wrote about occur again exactly the same way ?

 

I just tested the lines with air pressure for obvious leaks. Admittedly not the most detailed testing. Just what I could do in the shop quick and dirty.

My theory: On the flowbench the pump was taken apart, inspected, put back together, and then tested. 15.8 gpm @ 4,000 pump rpm with no load. 15.1 gpm @ 4,000 pump rpm with 100 psi pressure. I think once the o-ring settled in though, it lets air in between the housing and face plate. (still theory, but new o-ring arrived earlier today. I'll know tonight). When I got the pump back and put everything together, the engine fired up. BUT - the fuel level in the tank was higher than the pump. At the track Sunday the engine started right up again. BUT - the fuel level in the tank was higher than the pump. I did my burnout, stopped, and started backing up. Before the backing up was even complete, the engine died. Wouldn't re-fire. And now the fuel level was lower than the pump.

In the pits I took off all the lines leaving nothing but the line from the tank to the pump and could stare down into the pump. Hit the starter and could watch the gears in the pump spin. But no fuel. Even poured fuel down into the pump to prime it. Spun the engine and the fuel just glugged back down past the pump and nothing would pump out.

Last night I put duct tape around the outside of the pump and ran a line down from the pump into a bucket of water. Spun the pump counter-clockwise with a drill. Shot a full stream of water 18" into the air.

My hope is that a new o-ring will accomplish what the duct tape did and seal up the pump. Otherwise I need to find another 990 to do some back-to-back testing. This is driving me nuts.

Oh - and the first time it happened a week ago I did the burnout, backed up, staged, and went about 200 feet before fuel pressure went to 0. The difference was that this Sunday I fired up and ran for a bit before they shut me down because of an oildown in the shutdown area from the prior pass. I still had tons of fuel, but I think the level in the tank got lower than the fuel pump before I staged because of the additional excess idle time. But my tank is probably 60% full when it drops to the level of the fuel pump.

 

I have to tell ya , O rings don't "settle in" , there is something else affecting this as you say the pump performed on the bench-----it should perform on the car --

Unless you are overlooking something else --? I noticed you mention turning the pump counter clockwise with a drill ----- how is it mounted on the engine ?

Unless it is turned around to face the engine with it's cover (the pump) it should be turning clockwise -----maybe you have the wrong rotation pump ?