engine running rough at high rpm

[bpenkala]

Hello,

My m38a1 was running well (newly rebuilt carb just over 18 months ago), then one day drove to store and it was running rough and wouldn't develop power at higher rpm. I noticed a leaking fuel line at the fuel pump (line leading to carb from fuel) so I tightened that up (I have an aftermarket fuel pump without vacuum - less than two years old). After tightening fuel line the engine still does not run well when revved up (especially under load) and will sometimes just stall. I read the TM for troubleshooting and possible fixes but was wondering if there were any good suggestions where to start first (most likely problem considering my situation). Electrical is 12v. I checked spark plugs and they seem ok.

Thanks in advance!

[wesk]

It is always best to start with the troubleshooting checklist and follow it one step at a time. The chart was constructed by professional mechanics to insure no stone gets left un-turned. Yet the easier stones are turned first. This saves you both time and money.

When you ask for ten guys to offer up what they feel your problem might be and you start chasing their suggestions you are doing what we mechanics call "Shotgunning " the problem. It is usually a waste of time and will often cost more money.

Read page 79 of your TM 9-8014 carefully. They are offering you avenues down which to inspect and test to narrow down your problem to a specific system and finally to a specific component. The tough part for you is deciding what symptoms you have and matching them to sample symptoms in the manual.

I have been a professional mechanic since 1964. I do not always start in the troubleshooting chart but not because 10 guys suggested I check this or that. I start where my experience has shown me where I should start. Quite often the starting point is the few common simple tests we do to periodically check the overall health of our jeeps. They are compression check and a leak down test if the need is indicated by the compression test. Running the engine with a vacuum gauge and recording all readings. Checking fuel delivery pressure. Making a quick timing and dwell check.

At any rate the correct troubleshooting path is an ORGANIZED path!