The pump feeding my 4x4 is apparently far too large and is consequently heating the fuel up too quickly. I was thinking of running the smallest Walbro pump I could find, which is a GSL395 (130 lph). I'm getting conflicting data from researching online whether this is a suitable EFI pump or not. Some of the flow graphs I've seen show that it builds fuel pressure lower than required by EEC-IV. Anyone have any experience with one?

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'89 5.0L: 8.4:1 Dart 304, Crane 2031 cam, GT-40 lower, KB Blowzilla 2.2, LMAF, 90mm TB, 42# injectors, TwEECed A9L
'79 Bronco on 35s & 4" lift: 8.5:1 408M, Crane 523902 cam, GT-40 lower, Cobra upper, Cobra 70mm MAF, 65mm TB, 30# injectors, EDIS8, TwEECed A9L, single O2
'08 Buell XB12Ss: stock 10:1 1203, Drummer SS, '10 header, independent O2s, K&N filter, 3 bar MAP, DDFI3 tuned via TunerPro RT

Why do you think the pump is heating up your fuel too much?

We use way larger pumps on our builds all the time and don't have issues.

Fair enough, but the ambient temperatures around here are over 100*F. When relieving the fuel pressure at the rail (schrader valve), the fuel coming out was pretty hot. Regardless, my friend who is a fuel injection engineer happened to be with me and helped me diagnose the issue. The fuel was getting so hot that it was vapor locking the line; the truck eventually stopped running. There was also a substantial amount of pressure built up in the tank itself. I'll be getting a vented gas cap for sure.

The pump still works and the truck still runs, but the pump doesn't sound healthy anymore. I think it was damaged from the vapor lock situation so it needs to be replaced.

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'89 5.0L: 8.4:1 Dart 304, Crane 2031 cam, GT-40 lower, KB Blowzilla 2.2, LMAF, 90mm TB, 42# injectors, TwEECed A9L
'79 Bronco on 35s & 4" lift: 8.5:1 408M, Crane 523902 cam, GT-40 lower, Cobra upper, Cobra 70mm MAF, 65mm TB, 30# injectors, EDIS8, TwEECed A9L, single O2
'08 Buell XB12Ss: stock 10:1 1203, Drummer SS, '10 header, independent O2s, K&N filter, 3 bar MAP, DDFI3 tuned via TunerPro RT

Thought vapor locking was particular to the suction side of pumps when they installed by the engine. The lower pressure lets the fuel turn to vapor easier. Under higher pressure, it's harder to vapor lock (harder for fuel to vaporize) Are you sure that's what it was?

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85GT, 302 w/Dart Windsor Jr heads, Crane 2030 equiv. Performer 5.0, 75mm TB, 88mm slot MAF, 34lbs injectors, BBK shorties, 5spd converted to 4R70W with Baumann controller, 9" rear w/3.25s
A9L running A9P bin via Quarterhorse w/LC-1 WB

Understood, I think fixing the tank venting issue will solve the issue more so than anything but if the pump is damaged and needs to be replaced anyway so it is kind of a moot point.

As a note though, I have had cars shut off completely mid pass at the track because the pump couldn't suck against the vacuum in the tank anymore due to lack of vent.

Yeah, I think it was a combination of bad tank venting and very high ambient temperatures contributing to bad radiant heating of the fuel lines. I'll take a look at the fuel line routing near the engine and try to insulate it somehow.

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'89 5.0L: 8.4:1 Dart 304, Crane 2031 cam, GT-40 lower, KB Blowzilla 2.2, LMAF, 90mm TB, 42# injectors, TwEECed A9L
'79 Bronco on 35s & 4" lift: 8.5:1 408M, Crane 523902 cam, GT-40 lower, Cobra upper, Cobra 70mm MAF, 65mm TB, 30# injectors, EDIS8, TwEECed A9L, single O2
'08 Buell XB12Ss: stock 10:1 1203, Drummer SS, '10 header, independent O2s, K&N filter, 3 bar MAP, DDFI3 tuned via TunerPro RT

Sounds like you have a good all around plan and will get it fixed in no time.

Thanks, but I'm still unclear about the GSL395 pump. Is it suitable for high pressure EFI or not? I have a spare 255 laying around and then this dying 190... I'm sure it'll work for a little while but don't want to be stranded somewhere because of this issue.

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'89 5.0L: 8.4:1 Dart 304, Crane 2031 cam, GT-40 lower, KB Blowzilla 2.2, LMAF, 90mm TB, 42# injectors, TwEECed A9L
'79 Bronco on 35s & 4" lift: 8.5:1 408M, Crane 523902 cam, GT-40 lower, Cobra upper, Cobra 70mm MAF, 65mm TB, 30# injectors, EDIS8, TwEECed A9L, single O2
'08 Buell XB12Ss: stock 10:1 1203, Drummer SS, '10 header, independent O2s, K&N filter, 3 bar MAP, DDFI3 tuned via TunerPro RT

No need re-inventing the wheel here, people use the 255 pump all the time, fix the vent issue, double check your lines aren't routing too close to heat sources, put in the 255, and call it a day.

Yeah, alright... fair enough. Thanks.

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'89 5.0L: 8.4:1 Dart 304, Crane 2031 cam, GT-40 lower, KB Blowzilla 2.2, LMAF, 90mm TB, 42# injectors, TwEECed A9L
'79 Bronco on 35s & 4" lift: 8.5:1 408M, Crane 523902 cam, GT-40 lower, Cobra upper, Cobra 70mm MAF, 65mm TB, 30# injectors, EDIS8, TwEECed A9L, single O2
'08 Buell XB12Ss: stock 10:1 1203, Drummer SS, '10 header, independent O2s, K&N filter, 3 bar MAP, DDFI3 tuned via TunerPro RT