cohbra

iTrader: (13)

Recently I have experienced an issue with one (or both) of my Walbro fuel pumps so I thought I'd start a post to see if anyone has any idea what the issue may be, or has experienced it themselves.

The first time I noticed it was last week when I took the car for a long drive up to Ft. Collins. It was around 100*F that day and everything seemed fine on the drive up. However, when I started my car after letting it sit for about half an hour to drive back home, I noticed one (or both) of my pumps was making a very loud whining sound and my fuel pressure was a little low. My AFR's were still okay on the way home because I currently have it tuned to run a little rich during my break in period.

At this point, I assumed that I had another bad fuel pump and expected that I would end up having to order a new one. The next morning I started the car to see if I could figure out which pump was the issue and both were working fine again. Both pumps continued to work okay for several days (on short trips) until this last weekend when I took a drive out to High Plains Raceway.

Just as before, it was around 100*F outside and the car ran great all the way out to the track which was around 90 miles or so. After roughly 4 hours I started the car up to head home and I had the exact same symptoms as before.

Has anyone else experienced this, or do you have any ideas what may be causing it? I can also add that both times I had well over half a tank of gas, and I know my fuel filter is clean.

RotaryEvolution

iTrader: (30)

check the socks and the fuel pump hose between pump and body for cracking.

i haven't experienced that issue before and have run them up to 450whp(single pump) and juicing them up to nearly 20volts regularly.

cohbra

iTrader: (13)

It is a new fuel line so I know it's not cracked and there aren't any leaks anywhere. The socks are clean as well because I've had them out many times over the last few weeks fixing an issue with my fuel level sending unit.

It almost seems as though one of the pumps is cavitating due to heat somehow.

RotaryEvolution

iTrader: (30)

that is what it sounds like, but question is why? check the pumps thoroughly and you will probably find the answer somewhere. make sure the tank isn't completely sealed either or it may be going into a vacuum when the car is cooling off.

rxspeed7

iTrader: (5)

pumps were overheated, the cavitation and high pitch whining is from the fuel turning into vapor as soon as it hit the internals of the pumps and vapor locking the motors.

cohbra

iTrader: (13)

So have you personally seen this before rxspeed7? If so, how did you fix it?

It doesn't seem very likely to me that the pump would be hot enough to vaporize the fuel when it has been submerged in the tank with the car parked for 4 hours. I am pretty certain it is cavitating though, I'm betting it is most likely an internal issue with the pump.

One other thing that I thought about was to check and make sure there is enough clearance between the filter socks and the bottom of the tank since I'm using the CJ Motorsports dual fuel pump assy. It is possible to have the pumps inserted to a different height with this assembly. I'll update you guys if I find anything there.