Help Chasing Erratic Idle Please
01-07-2019 | 08:24 AM
#41
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From: Hemlock, MI
I've been working on this for over the past year with scans etc. Upon the advice of another member today I pulled the vac. line to the fuel pressure regulator while the 1k rpm surging was taking place and it immediately stopped the surging. Even though fuel pressure reads good with the vac line attached at all times, including during surging I may be leaning toward replacing the FPR. I will update the thread with my findings.
Keith
Keith
I think you are on the right track.
01-07-2019 | 08:07 PM
#42
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From: Atlantic Southeast
I was having some hard start/surging idle issues on my 502 MPI although it is a Mefi3/cool fuel model. Chased TPS and IAC first. Checked Fuel Pressure and found to be only 30 psi, regulator was bypassing and pump wasn't building any static pressure and bleeding off quickly. Replaced regulator and instantly idled and started cold with touch of the key. Didn't miss another beat all season.
I think you are on the right track.
I think you are on the right track.
Keith
02-17-2019 | 02:50 PM
#44
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From: KY
The VST plenum flooding comes into play after a warm engine has sat for a period of time allowing fuel to percolate out of the aged VST internal diaphragm thru the yellow hose and into the plenum.
My prior build used the VST and I removed it with current build. The VST is prone to vapor lock, and mine did VL at times, but no time was fuel present in the line
Your pressure is 37 psi, and when black smoke comes there is no fuel in the over flow line?
02-17-2019 | 10:54 PM
#45
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Don't agree, at no time should fuel be in the yellow hose.
My prior build used the VST and I removed it with current build. The VST is prone to vapor lock, and mine did VL at times, but no time was fuel present in the line
Your pressure is 37 psi, and when black smoke comes there is no fuel in the over flow line?
My prior build used the VST and I removed it with current build. The VST is prone to vapor lock, and mine did VL at times, but no time was fuel present in the line
Your pressure is 37 psi, and when black smoke comes there is no fuel in the over flow line?
02-23-2019 | 11:13 AM
#46
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From: Atlantic Southeast
Not sure how the VST came back into play but it was fully rebuilt less than 60 hrs. ago which is about 2 years. I also use non-ethanol fuel and the issue will happen prior to shutting the engine off. I have new yellow hose and zero liquid in it.
Keith
Keith
02-27-2019 | 02:48 PM
#48
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From: Atlantic Southeast
Keith
04-19-2019 | 08:44 PM
#50
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From: Atlantic Southeast
I see in the manual where the VST equipped engines are to be between 34-36 and cool fuel 28-32. For what it's worth the other engine is at 30 psi and runs fine.
So I'm guessing the thinking now is both VST electric fuel pumps are on their way out?
Last edited by Tractionless; 04-19-2019 at 08:52 PM.
