fuel pressure loss

[BlackoutDrunk]

Put a new DW pump in my car last week. Today I rolled into the throttle to pass a car and my car fell on it's face. Went lean and when I pulled over and popped the hood I found my fuel pressure was like 20lbs line on. I messed with the fuel pressure regulator and that didn't help much. I shut the car off looked for obvious problems (no fuel leaking and wires look tight) and when I turned it back on the pressure went very high (from me messing the FPR) so I adjusted it back to 42lbs line off and now I'm scratching my head. What could have caused that to happen? Electrical problem? After shutting the car down it holds fuel pressure for awhile.

I have a hot wire kit on the car and when I had the tank down to change the pump everything looked good. The night I changed the pump the car ran great no problems at all.

Ideas?

 

[Roger]

The rubber hose on the pump to the steel line may have ruptured.

 

[BlackoutDrunk]

That's not what happened. I think it might have to do with settings on my chip being out of whack. I'm still not exactly sure what happened but the car has been fine since. Very weird though. I've driven it a few more hours since then and even did a couple of WOT blasts and no problems at all.

 

[Slow91z]

That's not what happened. I think it might have to do with settings on my chip being out of whack. I'm still not exactly sure what happened but the car has been fine since. Very weird though. I've driven it a few more hours since then and even did a couple of WOT blasts and no problems at all.

I'm not going to try to tell you what did happen (cuz I don't know), but I can tell you for sure what didn't happen...It had nothing whatsoever to do with your chip settings because they have no affect on fuel pressure.

I would be scared of my new pump if that happened to me, but other possibilities include clogged sock (did you see any rust floating around in your tank when you did the pump change? Possible that big pieces of rust/crud stuck to the sock pulling the pump down and when you shut it off they fell away again temporarily.) and unknown voltage drop, but I can't imagine how low the voltage would be to only make 20 psi.

 

[BlackoutDrunk]

When I had the tank down it looked clean in there (tank was replaced at some point before I got the car), no rust or debris of any kind that I could see. I think I'm going to drop the tank and take another look around in there to try and figure out what happened.

 

[turbofabricator]

Just last night I removed the tank of a car with the DW pump in it. It wouldn't hold pressure above 50 psi at WOT. (StageII with TA heads) upon removal of the tank and sending unit, I found that the rubber hose had slipped off of the outlet line. I had to cut a section of the hanger to install the pump. I used zip ties to hang the pump and it had slid down about 1/4" causing the upper connection to come loose. It would hold pressure fine up to about 700 H.P but is ended up melting the spark plug on #5 cylinder and plasma cutting the exhaust valve and sending shrapnel through-out the engine scoring cylinder walls. The car ran a 10.03@134 with fuel pressure being off. So, trying to diagnose the fuel pressure issue, I found the hose loose. Good news. (not good news for the engine though.:frown Installed a longer hose and added more ties to hold the pump up. Now it should make the needed fuel. I had to THRASH and assemble a 109 block with GN1 heads for the car owner so he could race at Turbo Thunder this weekend. (Pacific Raceway). We'll see what happens with only 235 cid vs. 274 cid.

So.............if you drop pressure, check the in-tank hose connection. The DW pump is a little trickier to secure to the hanger than a Walbro pump. I had to cut about 1/3 off of the lower "ring" to get the supplied sock to clear. I also had to bend the sock up to install in the tank. It does fit, though.