70 911E using lots of gas?

[david482]

I have been working on this project for a while and have recently been able to really start to drive it. It starts and seems to run very well. I am truing to figure out why I am burning through gas at a very fast rate. I have probably gone about 20 miles and had the car idle for a bit but it has burned about 6 gallons of gas, it seems to be pretty consistent. I have not been able to find any gas leaks and so I am wondering what I should be looking at. The oil seems fine and once the car is running no real smoke to speak of. I have a little backfiring on decel because I think the RPM transducer is not working (could that cause that much gas to be used?) Any suggestions would be great.

[john walker's workshop]

MFI and good mileage are an oxymoron. they're a rich running system. not as bad as yours of course. is your preheat hose attached from the heat exchanger to the pump t/stat? won't lean out if it isn't. get it on a gas analyzer and see what you have. they need to run on the rich side as mentioned, like 6% idle and mid range or you will have idle and transition problems.

[Scott at Pelican Parts]

My '71 E runs really well. For comparison, I get about 12mpg in the city, and about double that on the highway.

[Zeke]

20 miles is not enough to gauge whether you are depositing some gas in the oil. And, when the oil is warm enough, it evaporates the gas. So one run at 20 mi has two things working against you AFA diagnosis. Do as JW say and fine out the mixture first. Also, check your plugs. Shoot, check you entire ign sys to be sure you're spot on.

[dtw]

Check, Measure, Adjust. Do not pass go, do not collect $200, go straight to CMA.

http://www.pelicanparts.com/techarticles/911_MFI/MFI_check_measure_adjust.zip

[appbiz]

webbers are in order perhaps...... I never could get the MFI right on my early cars

[frogger]

Originally Posted by appbiz

webbers are in order perhaps...... I never could get the MFI right on my early cars

NO! And Webers are no gaurantee if they are worn. The Check Measure Adjust (CMA) procedure is great, but it requires you follow along faithfully through all the steps. Backfiring sounds like it's too rich, but that could be because of injection pump adjustments or the microswitch being out of adjustment (or defective) or other problems in you setup. Once again, use CMA to set it up. Post questions here if you aren't sure of something and you'll receive plenty of help. A well-tuned MFI engine is a sweet thing. Mine gets around 20mpg on the highway and pulls strong. Good luck.

[fbarrett]

There's nothing as sweet as a nice MFI engine. My '70 911E once had a brief problem running super-rich, and it was simply a broken clip on the rod inside the FI pump. That was 20 years ago, so I can't recall the specifics, but it was an easy fix. Hie thee to a good MFI mechanic.

[Grady Clay]

David,

That kind of fuel consumption most likely is the cold running thermostat being full-on all the time. That usually is because the heat from the left heat exchanger isn’t getting to the thermostat to timely turn it off.

Is the thermostat very hot to the touch after some driving? Be careful, it can burn you.

Of course there can be other causes and various malfunctions, the result is the same.

Regardless of the cause, this fuel rate must be diluting the oil with gasoline. Smell in the oil fill. How thin is the oil on the dipstick? If you even suspect serious oil dilution, change the oil asap.

The issues with gasoline diluted oil are very poor lubrication (first to go is the cam-to-rocker) and (most important) when the engine gets hot, it boils off the gas leaving not enough oil to lubricate the engine. Rod bearing failure soon follows $$,$$$.00!

Frank, I’ll give you a call in a few.

Best,
Grady

[gulf908]

....webbers are in order perhaps......

this is NOT an option...
The MFI WDP will come to get you Bob....we know where you are....

Cheers,
Dennis.

...you should have lots of local help in your area ?...

[Jim727]

We have a WDP??? I knew I joined a cult, and was thinking we *needed* a WDP.

Cool. Sign me up!

[Grady Clay]

Excuse lame old me, what is WDP?

I agree, too many MFI owners opted for carburators when their MFI could have been properly brought into specification. This was mostly pre-Pelican. Today many are reconfigurating back to MFI.

I still want to know that your thermostst is hot.

Best,
Grady

[Jim727]

Grady -

WDP = World Domination Plot.

Having just converted my 2.2T to a 2.2E with MFI I'm learning why MFI has a cult-like following. It's intoxicating. Even though it's not completely dialed-in yet, I love it and I don't think I've turned the radio on since the conversion.

Jim

[304065]

WE walk among you.

[Jim727]

YES!!!

Mine has 2 solenoids - can I still play???

We need stickers.

Jim

Oops - sorry. Back to fuel economy.

[Jim Richards]

[Jim727]

Jim -

w/ 2.7RS-spec "lump" ??

[Jim Richards]

Lump is good. Run's fine, Jim.

[gulf908]

...Excuse lame old me, what is WDP?...

Grady,

I always thought of you as the Grand Wizard of this MFI cult....

Cheers,
Dennis.

[Grady Clay]

Dennis,

While I may know a little bit about original MFI, I'm not always up on the current 'dingo, lingo, logo'
The good news I'm not embarased to ask. Just dumb ol' me.

I never thought of MFI as 911 SCWDP like.

Best,
Grady