Something's up with my engine, and I have no clue what it could be. When I accelerate hard, the engine will go through first gear fine, but almost immediately after getting into second, it'll lose all power for a half second, regain all it's power, lose it again, etc. It's like I was pumping the gas pedal or something..

It's a 1986 LG4 with no computer controls, just replacced the plugs gapped to .045, ignition timing is 4* past spec, open element, no cat, and I am right in the middle of a rockerarm/spring change. Driver side bank is done, passenger side isnt yet.

Ideas? I dont even know what to check first..

 

Most likely you're losing fuel pressure. And this is quite common with older LG4's. Replace the pump and filter.

 

Maybe. But I just replaced the filter.

And I did more experimenting on the way to work today, and realized that it only does it when the engine is warm..

 

And?????

You could install a fuel pressure gauge and watch the pressure drop before you replace the pump. Or you could do what I tell most not to do and throw parts at it. There's a very, very good chance that this is related to a weak fuel pump. In fact, I'd bet on it!

Only happening when warm would also indicate a fuel problem. Most QJets do not feed fuel to the secondaries when cold. The fuel demand increases SUBSTANTIALLY when the secondaries are allowed to operate.

 

Yup, that would be from fuel delivery problems.

Either the pump is bad, the filter is clogged (remember, in a Q-Jet, the filter is in the carb's fuel inlet nut), or crusties built up in the gas tank plumbing.

 

I have a Q-jet but it's not a CC model. It's bone stock and a Cdn. version for emissions for 85. Dist. has a vac. advance.

Is this car a mechanical fuel pump or electric? Mechanical always leak from the breather holes when the diaphram rotts away. If you don't smell gas and can't see it leaking then I would bet the pump is fine.

When is the last time the filter was replaced? What are you running now for a carb? Did the problem show up right away with your new carb or has it been running fine with it for a while?

 

Sorry I havent gotten back sooner, I was at work and at school.

Anyhow, the carb, far as I know, is the orig. and could probably use a rebuild. Secondly, the fuel filter is a week old. Just replaced it in hopes it would be going away. I should actually look into rebuilding mine or something. Need to learn how to set up a rebuilt one, and I know I should richen the jets a bit too.

Ok, well I guess I will look into a replacement fuel pump. I'd be willing to bet that mine is the origional, so it should be replaced anyway.

Oh, and this problem sort of phased it's way in. I noticed it do that once or twice before, but now it's happening more and more often.

Thanks for the help btw.

 

Go ahead and replace the pump. It's dirt cheap. Like $20. I doubt it's the problem tho. The carb likely needs adjustment or a rebuild. One of the only things left that I am afraid to tinker with. Rebuilding carbs and rebuilding trannys. I'm game for anything else.

 

i would replace whats is less expensive, either way your going to have to replace it sooner or later. just depends when your car breaks down on you like mine did.

 

Well I'll see about replacing the pump next week, and I have been looking at reman carbs from SUmmit.. Some start at $175...

 

Ok, so, for my engine, what PSI and gph should I look for in a fuel pump?

 

Stock

Don't waste your money. The pump that's on there will feed at least a 400 HP motor. You'll never need any more pump as long as you have a 305.

Just go to AutoZone, spend $12 and 10 minutes, and see if it's better.