Gonna look at the filters when I get out of work today. The fact that its just a pulse of loss is worrying. Almost like it could be drivetrain as well.

Pulse of loss? Like just briefly and then power comes back? Mine is doing that but I know its a fuel starvation issue....

(07-09-2010 10:15 AM)Captain America Wrote:  Pulse of loss? Like just briefly and then power comes back? Mine is doing that but I know its a fuel starvation issue....

Yep pretty much. Guessing filters or air in the line.

There should only be air in the line if there were some sort of restriction somewhere. Air would "appear" right after the restriction from the vacuum produced at that point then travel all the way up to the fuel pump.

I've got something similar going on... I don't drive the car WOT ever because I don't have a pyrometer yet but I will mash the peddle for a couple seconds at a time on the freeway every once in a while and when I do boost comes up, flattens, drops off, then comes back up... all within a couple second time.

Gotta be fuel I'm thinking, you and me.

I want to put a fuel pressure gauge inline after the lift pump to verify

Because my elements are all maxed out I think that I am not getting enough pressure at idle as well (lopes a bit).

http://www.harborfreight.com/fuel-inject...92699.html This should work right?

Its probably something simple, but the fact that I cant get it to happen with the car parked is worrisome.

Gonna be difficult to monitor pressure while driving unless you have a long line connected to the gauge.

Which car is having the trouble?

Guess you've got a modified pump huh? I don't know much about the pumps yet.

It happened again in the parking lot at work and not again since then.

Air in the lines can do that. Accumulating a bubble until its big enough to get sucked through and start over. Check your tank hose.

I did replace one of the tank hoses a few years back. If it was a gasser I would say it was skipping. Going to get a cheap fuel pressure gauge this weekend and run it into the cabin. It is VERY possible the lift pump cant keep up.

I tightened the tank hose and it seems a little better but it still is acting like it is missing. I am going to try replacing the tank screen.

Gonna swap to and fro lines first and see how that goes.

(07-09-2010 01:48 PM)Captain America Wrote:  I want to put a fuel pressure gauge inline after the lift pump to verify

A vacuum gauge before the lift pump would probably tell you more about the restriction vs the lift pump output.

I had both on my earlier car, and the restriction would creep pretty high before any loss of pressure showed on the lift pump output. And if you sucked air, the lift pump would jump around in pressure, instead of any consistent reading. Reading a vaccum gauge with a clean fuel line and in tank filter, its around 5 inches of mercury.

I started to notice a power loss above 10-15 inches of mercury, and the lift pump would drop down to 10-15 psi. This was on a high mileage fairly tired motor though.

My fuel tank produces a pretty good vacuum as its drawn down, but the engine doesn't see any power loss from it. Its been one of those "I'll get to it" things because it hasn't caused any trouble.

Ok well wouldn't the goal be no vacuum in the tank? If there was a vacuum I would say that's a problem....

My 617.931 ( 300GD)/ M - IP is doing this kind of pulse when in 3rd at 2500 rpm I stop acceleration for a while and after that press accelator . Its strong if I press it deep. After two "balances" it goes like a slow rocket. Iddle is ok at 650 rpm , full load ok , top speed ok.....
May be only a time lag between injection and cilynders possition?????

I believe now it is a sticking valve causing compression loss. When I replaced my valve stem seals I noticed that one of the valves was sticking. Last night I heard what sounds like valve hitting a piston. Time to look for a new head.