madkaw Posted June 10, 2009 Share Posted June 10, 2009 Guys I need help. I installed a Walbro thinking my stock fuel pump was failing in my stock 81zxt. I know I did this backwards but I installed(that I just purchased) a guage in line to test fuel pressure. Turning ignition on primes pump and the pressure goes off the scale of the 100psi guage. When I start the car the pressure remains high off the scale and after the a few seconds the pumps starts to whine like somethings not right.(I then shut it off) I earlier pulled the return line from the before the FPR, and I disconnected it at just before the tank ,and blew air threw it and it was clear. Should I suspect my fpr is bad? The car was dying mostly in a decelerating condition, and the stock pump would whine like it was clogging or cavitating. The car will start right up and idle good initially. Any suggestions would be appreciated Quote Link to comment Share on other sites More sharing options...
Challenger Posted June 10, 2009 Share Posted June 10, 2009 The car was dying mostly in a decelerating condition, and the stock pump would whine like it was clogging or cavitating. The car will start right up and idle good initially.Any suggestions would be appreciated This is all before you installed the walbro right? Just checking. Any way to plum the guage in after the fpr to see if its actually opening? If its closed then youd get insane fp numbers. Just a guess. Also what kind of gauge did you buy and how did you mount it up. Just curious. Quote Link to comment Share on other sites More sharing options...
madkaw Posted June 10, 2009 Author Share Posted June 10, 2009 I bought a Actron fuel pressure test kit and it is a 100psi guage. I installed the guage on the return line and I get the same reading-basically off the scale. I would think hooking in line with the return line would suffice being after the FPR-right? The fuel pressure reading are AFTER the Walbro install. The Walbro pump is doing the same thing as the stock pump-- as far as making noise after a few seconds. I didn't have a guage to test my stock pump so I ordered the Walbro on a guess that it was the problem. I was obviously wrong. The guage was to help determine whether this is a cavitiation or a blockage of the fuel line. I would say that I am not cavitating. Quote Link to comment Share on other sites More sharing options...
madkaw Posted June 10, 2009 Author Share Posted June 10, 2009 Would you believe that the return line was clogged in the fuel sending unit. After seeing the 100psi on the return side i know I missed something. I have had that same fuel sending unit out probably 3 times and you can see by the pic that it looks brand new. You will also see where I cut the return line to get at the obstruction. I cannot tell you exactly what it was, but I am betting it was somekind of muddgobber from a bug who built a nest in there. I couldn't get at with a piece of wire because it was in the curve of the pipe, so I just cut it off. The passage was completely blocked off, I don't know how the car ran this long Quote Link to comment Share on other sites More sharing options...
jc052685 Posted June 11, 2009 Share Posted June 11, 2009 Thats what i was thinking 2 seconds into your 2nd post. glad you got it. Quote Link to comment Share on other sites More sharing options...
Challenger Posted June 11, 2009 Share Posted June 11, 2009 Glad you found it. Im suprised at 100 psi id didnt pop out. Good thing to do if your having fp issues is hook up an air compressor to the return line. Bubbling noise is good. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 14, 2009 Share Posted June 14, 2009 Would you believe that the return line was clogged in the fuel sending unit. After seeing the 100psi on the return side i know I missed something. I have had that same fuel sending unit out probably 3 times and you can see by the pic that it looks brand new. You will also see where I cut the return line to get at the obstruction. I cannot tell you exactly what it was, but I am betting it was somekind of muddgobber from a bug who built a nest in there. I couldn't get at with a piece of wire because it was in the curve of the pipe, so I just cut it off. The passage was completely blocked off, I don't know how the car ran this long I would, I have seen the EXACT same thing in my Fairlady Z, and about half a dozen other cars that have sit idle for a time, and then were put back into service. On my Fairlady, I had replaced EVERY bit of fuel hose EXCEPT for the return line back at the tank (one, because I ran out of it) under the assumption 'Hey, it'sa return line, how much pressure can be in it?' Fired it up, revved a couple of times to keep it running because it was running a bit rich, then it cleared up all of a sudden. Confident it was just something from 'sitting around so long' I let it idle. Idling I could smell a raw gas smell, REALLY strong. Couldn't see anything, but MAN it was strong. Figured better go to the shed to grab a jack to look underneath, even though I couldn't see anything on the dirt under the car. As I went behind the car, I was REALLY strong gas, and I thought I heard a faint 'HSSSSSSSSS' Looked up under the tank, and there was a stream of High Pressure Gasoline streaming to the ground. Looked under further---yep, the return line! The ONLY one I didn't change. Had pulled it and blown down it with compressed air, same as you... but the plug was in the tank return line. Curiously, my sons' 510 wagon had this in the return and the feed lines. WE had filled the car and run it to 3/4 tank with some 100 octane throwoff gas we had after the season ended, figuring it would sit and it was better to use the gas there than in the lawn mower... Months go by, and we go to try a restart...no go. No gas, no return line. We KNOW it was clear when we put the SSS carbs on it. Drop the tank, and all the sludge from the old gas had been solvented loose by the goo 100 octane stuff and it's vapors, and then clogged BOTH lines. Worked the stuff out with the standard coat-hangar and vice grip method. With the tank drained, it was off to an undetermined location whereby hot sudsy high pressure water was applied to flush out any remnants of the evil varnish gas residue and clingy stuff on the tank insides... Frank 280ZX had a similar issue with his 280ZX®. We had replaced the fuel pickup like shown in the photo as the car was parked with a full tank of gas, and then was let to evaporate over 14 years+ in storage. New pickup and it ran great. But going down the road something was happening. Damnable thing. But it ran at idle and freerev fine. And as long as there wasn't a big load on the car, it would go on like nothing was amiss. The fresh gas in the tank had solvented the brown goo and it sloughed down to cover the pickup transfer holes in the baffles arouud the swirl pot. Get on it, and the fuel flow was sucking the in-tank swirl pot dry! Another case of 'Take it to the Dutch Cleaners' for an inexpensive fix... Tank looked like new inside once cleaned out! Same as the 510. Quote Link to comment Share on other sites More sharing options...
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