MFI troubleshooting - high idle, pops and bucks at part throttle

[Arne]

Even later addition - The check valve is in fact inside the barb fitting, not either of the banjos. Mine is present, but is pretty much toast. It was being held part way open by chunks of the phenolic material, and sticks wide open when pushed. Doesn't go back to the "closed" position by itself, either. So I need to replace it. No purpose in going any farther until that is handled.

[edmayo]

We last bought those a couple years ago, readily available then, expensive, but available. I always carry a spare in my travel kit. Sorry, didn't mean to mislead by saying 'banjo' I knew what I meant !!

[Arne]

Still expensive, but still available. Should be here later this week. No further work on this part of the car until then.

[tcsracing1]

I am currently experiencing similar problems with my 1972T.

I pulled the car out of hibernation in 2017. (been parked since 1986)
I had all the lines/filters replaced, tank drained etc. lots of oil in the exhaust. Car didnt want to run.

Then I had the plugs and points replaced and a new fuel pump.
The car would run but once warm it would stall and wouldnt start again.

I sent the MFI pump to MFI Werks and the car worked better but still have the problem of it sputtering once it becomes warm.
It will run when it is cold, but soon as it gets up to temp it will not run. It sputters and stalls. i was lucky to make it home.

Would it be a matter of just adusting the MFI? Or is there something else going wrong here?

[Arne]

I am currently experiencing similar problems with my 1972T.

I pulled the car out of hibernation in 2017. (been parked since 1986)
I had all the lines/filters replaced, tank drained etc. lots of oil in the exhaust. Car didnt want to run.

Then I had the plugs and points replaced and a new fuel pump.
The car would run but once warm it would stall and wouldnt start again.

I sent the MFI pump to MFI Werks and the car worked better but still have the problem of it sputtering once it becomes warm.
It will run when it is cold, but soon as it gets up to temp it will not run. It sputters and stalls. i was lucky to make it home.

Would it be a matter of just adusting the MFI? Or is there something else going wrong here?

Sounds like the exact same symptoms my car has. Runs OK when cold, and very badly - bucking, sputtering and dying - when warm.

My first advice (based on recent experience) is "do not touch any MFI adjustments". Chances are there is something more basic at fault.

I don't know yet if the bad fuel return check valve is the cause of my problem, but I have high hopes. I've heard from others now who had failed check valves, they experienced similar symptoms. Mine will be here later this week.

In the meanwhile, it might be worth taking a look at the one on your '72. See if it is sticky, or stuck partially open like mine was.

[tcsracing1]

Sounds like the exact same symptoms my car has. Runs OK when cold, and very badly - bucking, sputtering and dying - when warm.

My first advice (based on recent experience) is "do not touch any MFI adjustments". Chances are there is something more basic at fault.

I don't know yet if the bad fuel return check valve is the cause of my problem, but I have high hopes. I've heard from others now who had failed check valves, they experienced similar symptoms. Mine will be here later this week.

In the meanwhile, it might be worth taking a look at the one on your '72. See if is is sticky, or stuck partially open like mine was.

thanks, i will take a look!
Would be nice to finally drive the car!

[Arne]

Check valve arrived today. Now installed, I think I may be finally making some headway.

Except...

I now (or probably still) have another fuel delivery issue, and it's a bit odd. Was apparently doing this prior to the check valve replacement, but the general lack of reliable fuel pressure made it hard to notice.

Here's the deal, it runs pretty well (given that the mixture settings are all screwed up) when on the flat or going down hill. But go up much of a grade and it starts to run out of fuel. The steeper the grade, the faster the starvation happens.

I can't think of anything or anyplace in the fuel system that could do this, other than in the tank. Yet the tank was really clean inside when I popped out the sender to peek about.

The tank does have a big dent in the bottom from some bozo and probably a floor jack sometime in the distant past. Not dented near the outlet.

Am I missing something here? Is there anyplace other than the tank I should be looking?

If not, I'll pull the sender again, put the front end in the air and look inside. Not sure what I'll find, but I can't think of where else to look.

[Arne]

Getting more confused as I go.

Putting the front wheels up on a pair of 8" (20cm) ramps is more than enough to trigger the problem. With the front that much higher than the rear, the car will not start. Put it back on the flat, it struggles a bit (as though it has to prime the fuel system) and then fires. Fuel pump sounds different briefly before it starts.

While up in the air and not able to start, looking in the tank shows nothing at all different than before. Tank looks really clear and nice. Nothing blocking the tank strainer.

Are there any check valves in the factory fuel pump?

[edmayo]

Just simply remove the feed line from the discharge of the pump which goes up thru the frame section right where it enters the inlet fitting of the fuel filter console. Install a pressure gauge there and see if you're getting 30 psi or so of pressure, then run that hose into a small coffee size can and the pump should fill that in less than a minute. If it does all that then jack up front of car and repeat. If it fails that then fill a five gallon can with gas and with several feet of extra fuel hose run the car at an angle from the five gallon can. This will prove whether it is a pump problem or a fuel feed problem involving the car's gas tank and lines. And by the way make sure that the fuel hose from the bottom of the filter is going to the passenger side of the MFI pump, and the driver side of the MFI pump is going to the inlet fitting of the console. ( the fitting facing rear of car)

[stephers]

Hi Arne

Been watching this thread from the start and perhaps a couple of things. I don't see anywhere where it says that you have actually measured the fuel pressure with a gauge, both at idle and at a higher rpm. Also, I have seen pumps over the years put out enough pressure but not enough volume, again, both at idle and higher rpm. Ed referred to volume in an earlier post but saw nothing else about that. Going any further without really knowing and confirming both would drive me crazy. It is about basics, it sound like you are just not getting enough fuel.

Thanks, Rick