Weird fueling problem

[shackwrrr]

been messing with my van and I've run into an issue where it leans out badly at 20psi. I tried the pinch test and it built 80 psi pretty easily. I know 80 is low but at 20 psi it should be sufficient I thought.

Well I replaced some hoses, clamps, and fuel filter. That didn't help. Today I decided to do some more tests, I taped the gauge to the windshield and went for a drive. The stretch of road I use isn't long enough to make it to 20 psi (boost creep) so I did 15psi pulls watching the gauge. I didn't notice much amiss until my last pull where it started to lean out pretty bad and the knock lite came on, the fuel pressure had dropped to 60psi at 15psi of boost.

I got back home and did the pinch test again and it went right to 80 again, this time though I kept holding the line and seen the problem, it started dropping. The longer you hold pressure the lower the pressure drops, if I held it long enough the fuel pressure drops to nothing.

So what would cause this? Windings in pump overheating, brushes, bad clamp in the tank?

Looks like I'll have to order a TRE pump this weekend.

[cordes]

I don't have any ideas which you haven't listed, but I'll be very interested to hear the actual cause. Thanks for posting this one up.

[zin]

As pressure goes up, volume goes down, so your pump may be capable of making 80PSI, but not deliver the needed volume at that pressure. To confirm, duct tape a gauge to the windshield and see what it goes to, it probably isn't holding pressure at that volume...

Mike

[shackwrrr]

In the second chunk of words I did run with the gauge taped to the windshield. The pressure was fine until about the third pull where it could only make 60 psi.

Pinch off the return and it goes to 80 then slowly drops off until there is nothing.

[zin]

Then it's either on it's way out or just isn't rated for the volume you need at 80PSI... Assuming the wiring is good and not "short changing" the pump on voltage... it is surprising how much difference a few volts will make on a pump's performance.

Mike

[shackwrrr]

I have a TRE on order, we'll see when I drop the tank.

[shackwrrr]

Got it replaced and no problems now.

I stuck the old one in some water to see what the issue was and I found that when it got under pressure it would pulse on and off. I tore it apart and I found that where the windings were crimped to the commutator there was lots of corrosion. There was no solder or braze, just copper crimped to copper.

[shackwrrr]

http://static.photobucket.com/player.swf?file=http://vid43.photobucket.com/albums/e357/shackwrrr/VID_20121217_092815.mp4

[shadow88]

TRE is a new one to me. What's it stand for?

[shackwrrr]

TRE is a new one to me. What's it stand for?

Basically a name brand knock off of a walbro. Supposed to be more reliable than the walbro.

[zin]

Weird... Guessing the pressure was causing an intermittent contact?

Mike