Air Bubles, Fuel Starvation and Stalling....Sometimes

[mingus1]

I have for several months had an intermitant problem with my '82 300D suddenly losing power and either stalling or nearly doind so. It usually happens at highway speeds and/or going uphill. I can drive it for several hundred miles without a problem and then have it happen again for the next 20 or 30 miles. Usually if I can shift it into neutral and pump the accelerator it will seem to clear up and run ok for a bit. Downshifting to a lower gear when possible, increasing the rpm, often works too. After dying on the Mass Pike, at night, in a section with no shoulder or breakdown lane and very nearly getting creamed despite having my hazards on, I have pretty much just been driving on local roads for the last month. This weekend it stalled on me on a flat section while doing 30 mph.

It will happily rev in neutral with no problems. I do however see tiny air bubbles in the primary filter and the level of fuel in there goes down.

I have replaced everything from the outlet of the tank to the primer pump, including the fuel line.. Both filters are new. My primer pump was leaking and I swapped it for one off my parts car which is OK. I will replace that one with a new one soon. I have checked and tightened all the hose clamps, which are the high pressure type.

The only thing I can think of is that the fuel tank strainer may be getting clogged? Before I go to the trouble of draining the tank and removing it I wanted to hear some thoughts on that.

I just remembered that the problem has mostly happened shortly after filling the tank, but not always.

Sorry for the long post - trying to cover everything.

BTW does anyone know why spell check didn't work on the first paragraph but did on the others?

[TMAllison]

I'd confirm once again no air is getting in from the filter back to the tank since you did work in that area. Then do the strainer.

[ajcbgray]

Before you pull the strainer swap the hoses where they connect to the supply and return hard lines under the hood. If the problem is solved then your strainer is clogged.
ben

[mingus1]

Originally Posted by ajcbgray

Before you pull the strainer swap the hoses where they connect to the supply and return hard lines under the hood. If the problem is solved then your strainer is clogged.
ben

Just to make sure I understand you correctly, I should put the cigar house on the supply line and use the return line as the supply, which will bypass the strainer when it draws fuel from the tank?

Am I correct in assuming that the problem must lie between the primary filter and the fuel tank or would an air leak in the supply line put enough air bubbles in the tank that they could be sucked into the supply line? I wouldn't think that would be the case.

[ajcbgray]

You are correct on the hose swap.

The air leak would be between the tank and the lift pump. After the lift pump the fuel is under pressure (not vacuum), so a leak would push fuel out not suck air in.

[mingus1]

Originally Posted by ajcbgray

You are correct on the hose swap.

The air leak would be between the tank and the lift pump. After the lift pump the fuel is under pressure (not vacuum), so a leak would push fuel out not suck air in.

Thanks.....I should have been able to figure out the second part on my own Never underestimate the power of frustration (and humidity) to muddle the thought process!

[mingus1]

That seems to have worked. At least I have a nice full, air bubble free, primary filter and no leaks. I'm thinking that means the supply (now return) line and connections are all good so the problem is the strainer in the tank. My still pretty new primary filter already has some black crud in it so that supports the strainer theory too.

Other than clogging my filters because I am bypassing the strainer is there any reason why I can't try driving home (about 50 miles) with it like this? I'd like to see how it goes on the highway and would also rather drain the tank, etc. at my garage where I have the proper tools.

[ajcbgray]

I've had mine swapped for a week or so with no problems. I'm not sure how high the return is where it enters the tank... you might have a problem if the tank got too low on fuel.

[mingus1]

Originally Posted by ajcbgray

I've had mine swapped for a week or so with no problems. I'm not sure how high the return is where it enters the tank... you might have a problem if the tank got too low on fuel.

That's easy enough to avoid. When I was under there last week I was surprised at how low it actually is - near the bottom IIRC. Every other car I've looked at has had it near the top.

Thanks again for your help. I'll brave the NYS Thruway with a bit less trepidation tomorrow.

[winmutt]

Dumb question. Do you get a woosh when you open the fuel tank?

[mingus1]

Originally Posted by winmutt

Dumb question. Do you get a woosh when you open the fuel tank?

Nope - already thought of that.