Fuel Pump Replacement on 1995 5.7 TBI

[tmothy07]

Update: that didn't solve the issue and I threw in the towel. I let Ace Marine know everything that I had done to it so far with no change in behavior and they dug into it. Turns out, it was a clogged valve/fuel line issue in the in-tank pickup. The material was what confused all of us, it looked almost like a gray concrete-y mud, and had hardened inside of the old hose and filter. It was evidentally causing a partial blockage sometimes (which accounted for the inconsistency of the issue). Any way, a new anti-siphon valve to replace the original, and a new hose/filter, and a nice clean fuel tank has the boat running like it's brand new. I suppose I don't have to worry about any fuel system part replacements for a while lol.

[tmothy07]

Thanks for that source Tim. I've got my replacement TPS, so hopefully that works to solve this issue.

[CantRepeat]

This is the MEFI 1.2 diag which I've been using on my 94. You might test the coil and the pick up.

MEFI 1-2 diagnostics

[ValveCoverGasket]

Think I need to have someone professionally check the injectors on this TBI 5.7?

I think it's worth doing and is really inexpensive. I don't think running cleaner through the tank is anything but a waste of money (imo) only takes a few minutes to pull them and send them out for cleaning and testing

[88 PS190]

There are only a few, engine coolant, idle air flow etc.

[tmothy07]

Sometimes the only solution is to figure out a real fuel pressure data logging solution. Not super cheap but useful.

Many generations of MEFI will allow you to disconnect a sensor and when disconnected fully the system will run off a "default" value so if a sensor is supposed to be reading say 1 to 5 volts - the unplugged value that is inserted might be say 3 volts. And that should be sufficient to provide a "normal" run condition or atleast faily normal.

Interesting, I'll have to give it a shot. Any idea where I can find a diagram for these sensors (or perhaps a TeamTalk post)? Or should I order a service manual?

[tmothy07]

I installed this pump on my LT-1 and its worked just fine.

https://www.highflowfuel.com/qfs-oem...aces-52365517/

Unsure of the difference with what OP used, but LT-1 does require higher pressure than the TBI.

Looks like the links (and multiple on their site) all go to the same pump

[Huckelfin]

Will this pump work for an LT-1? Also have a 1995 MC with 5.7L

I installed this pump on my LT-1 and its worked just fine.

https://www.highflowfuel.com/qfs-oem...aces-52365517/

Unsure of the difference with what OP used, but LT-1 does require higher pressure than the TBI.

[88 PS190]

Sometimes the only solution is to figure out a real fuel pressure data logging solution. Not super cheap but useful.

Many generations of MEFI will allow you to disconnect a sensor and when disconnected fully the system will run off a "default" value so if a sensor is supposed to be reading say 1 to 5 volts - the unplugged value that is inserted might be say 3 volts. And that should be sufficient to provide a "normal" run condition or atleast faily normal.

[tmothy07]

Seems like that pump has worked just fine for us (did a lot of skiing over the weekend). We are still getting an occasional hiccup/misfire/drop in RPMs on the holeshot, however, but that was present before and is what I'm ultimately trying to fix.

I've replaced the fuel filter, fuel pump (obviously), distributor cap, rotor, spark plugs, plug wires, cleaned the throttle body, and ran a bunch of SeaFoam for the injectors and HEET water remover through the tank and added fresh gas. I'm honestly stumped as to what could be causing this issue now.

Every once in a while it's extreme enough to not let the skier get up, but most of the time the rider barely feels it or it doesn't happen at all. It's definitely a drop in RPM, so I don't think it's anything to do with the transmission or drive shaft but I've run out of ideas for the fuel/spark system. Think I need to have someone professionally check the injectors on this TBI 5.7?

[tmothy07]

Haven't gotten it to run under load, but running it in my driveway out of a 5 gallon bucket yielded good results. It was able to rev all the way up and down while in neutral. As always, found another problem, I've got a small hole in one of my SilentMasters, so once that's patched up here in a day or so I'll finally get this thing tested under load!

The squealing noise from the previous pump is gone now, though, so there's that.

[tmothy07]

New pump primes just fine, so can't wait to finally get this job done.

[tmothy07]

Also a quick update. My pump isn't priming (I should've tested prior to hooking it up), and I'm contacting the company to try to get a replacement. I think I received a defective part.

Update: They put one in the mail for me today. Took about 5 seconds on the phone, their customer service was great.

[tmothy07]

Will this pump work for an LT-1? Also have a 1995 MC with 5.7L

I haven't actually been in a '95 with an LT-1, so I'm not familiar with it or if it may have a different pump. Maybe post up a photo of your current one if possible?

[walterlaughlin]

Will this pump work for an LT-1? Also have a 1995 MC with 5.7L