My 86 F250 302 EFI engine cuts in and out when I'm plowing snow and put a load on the engine. If I'm idling, or driving it without the plow down it runs fine. When I'm plowing snow and put a load on the engine, it starts cutting in and out, "chugging" if you will.....Someone suggested that I checkout the fuel reservoir, which I did. I ended up bypassing it and putting an in-line filter in and the truck still runs. Someone also suggested that maybe it is the catalytic converter being plugged? Don't know how I would trouble shoot that. If anyone thinks I should do that, let me know. I also know that there is a fuel regulator and it looks like it would be a bugger to try to get off of the fuel rail. Do these things ever go bad? Any way to trouble shoot it? In-tank fuel pump appears to be working, as well as the hi-pressure fuel pump. As you can see, I am out of ideas. Any help would be appreciated!!!

 

Are you plowing at high speed when it does it? I normally just do my driveway and a parking lot, but during one of these heavy snows I got scared I wasn't going to get out of my road, so I plowed it a couple of times at about 25mph, and noticed my belts would start squealing. I looked under the hood and snow was getting on the engine and the belts. I am wondering if your distributor cap is getting snow on it and causing the truck to miss-fire?

 

Could be that your alternator is having trouble keeping up when you move your plow. I've heard of trucks nearly shutting off under heavy load while plowing. Low voltage can make EFI do funny things! Do you have a heavy duty alternator?

 

I replaced the alternator about a year ago. Not sure what differentiates a heavy duty alternator from a regular one but keyul, if you can tell me that I will check it out. I hear what you're saying about the EFI. I replaced the EFI module this year as I thought that was the culprit when I first started experiencing the problem.

As far as Franklin's question on how fast I am plowing, I would say that the problem happens whether fast or slow. If snow was getting on the distributor cap, could it affect all 8 cylinders at one time to misfire? Because that's what it seems like it is doing.

I am leaning towards this being a fuel problem, and a pressure problem at that but I could be wrong. I bypassed the fuel reservoir and that has actually seemed to make the problem worse. This leads me to believe that maybe the in-take pump is not working properly and before I bypassed the reservoir there was fuel available for the hi-pressure pump to access. Now that I took the reservoir out, the low-pressure pump has to keep up or the hi-pressure pump will starve?

A friend of mine is going to lend me his fuel pressure guage so I can see what type of fuel pressure I am getting. I read a posted thread from someone who sounded like they had the same symptoms I am having and it was a fuel pressure problem.

Make no mistake, I am no experienced mechanic by any stretch of the imagination....just an engineer cursed with the propensity to take things apart when they don't work. So any and all suggestions are welcome and appreciated! I'll let you know when I test the fuel pressure, hopefully this weekend. Thanks!