2.4E Engine running problem advice Req'd

[mallen282]

My '72 911E has suddenly started running like a pig. I'm concerned that it's the MFI? The symptons are as follows:-

Cold start takes about 5 minutes feathering the throttle to keep it running and not stalling, then it idles kinda OK. Then, when it's initially under load it hesitates from 1500 revs to 2500 revs but it's fine when your foot is flat on the gas and pulls like a train......The problem gets much worse as the car warms upto operating temperature.....

TO try and fix the problem Auto2000 put on NEW SSI heat Exchangers and connecting pipes including the regulator pipe (with the flappy bit in it!). My Mechanic @Auto2000 checked the CO emissions which were reading 8% and adjusted them down to approx. 1.6% ??? The car was putting out 167BHP on a recent PCGB rolling road run at Silverstone so I'm surprised at this sudden illness. . . . . . . .

Any Idea's???????

I live just south of Cambridge, is there anyone locally capable of identifying the problem and ofcourse curing it (Auto2000 were reluctant to start messing with it!!!!!!!!) ???????????

Fanks in advance

M.

[veryporky]

Hi Mark,

Funny you should live just south of Cambridge because I do too!!! In fact so close it's a wonder I've not seen you coming the other way. Actually I'm S.W. of Cambridge in a place called Gamlingay. I met a bloke who runs a garage called Auto 2000 (somewhere over in the Bedford direction?) at the local pink fariies meeting near st ives. That was in the early '90s when I first had my old SC. Fair to say he had a bit of a know it all approach, however the tinkering with your car seems to indicate he may still have quite a bit to learn about these early cars. Whilst MFI is a bit of a black art by all accounts, (and I am a newbie as far as it is concerened!) I cannot for the life of me see what changing the heat exchangers might achieve to sort rough running. Perhaps they were thinking of the way it affects the warm up thermostat but that is a very long and costly shot!!! CO at 1.6% WTF? Watch you don't burn the valves!!! Have you they/been through the ignition? Plugs, points, leads, caps all need changing before you start with the MFI. In fact according to Check Measure Adjust, the MFI bible, the injection is the last thing you fiddle with. There is a copy on Pelican Parts which you should look at.

I'm a newbie as far as MFI is concerned. I have just nabbed some tuning gear off e bay so I can double check the basic set up before I pop my cars on the rolling road for fine tuning. Whilst I don't have the time and the inclination to rebuild your car I certainly don't mind helping you check the basic stuff. You might just find it's a plug that's out or something. Sounds like the thing was smack on when you dynoed it!!!! Drop me a line if you want.

[2.4TE]

8% at 2500rpm is probably about spot on. This guy you are using I think is no mechanic when it comes to MFI. He's just cost you a lot of money fitting SSI's and worse, he's adjusted the pump without evidence that it needed changing. You need to get the pump back to where it was then I would have checked the points first. PM me and I can send you the 'Check Measure Adjust' document. I think Autostrasse in your part of the country might be a better bet. Failing that arguably the best person in the UK is Russ Lewis at RSR Engineering in Surrey. Tel. 01428 602911

[mallen282]

Thanks guys for your advice.... Have sent Keith & Dr Dave PM's!

Note that I had the SSI Exchangers to put on anyway so it was a long shot really....

Hopefully, will be having play over the weekend to check the basics?? Although I'm pretty sure it's not electrical!

Has anyone had a early car sorted out by AUTOFARM???

Rgds

[domtoni]

MArk,

Read my last post on Pelican.
http://forums.pelicanparts.com/showthre ... ost2613653

Not sure what is causing it. I doubt your pump is at fault. Pumps usually don't go off, unless it was fiddled with by some previous "expert".

For sure the 1.5% is too low, and you seriously risk burning a piston.

I doubt that your electrics have gone off, perhaps your points have closed up a bit?

If you look at your MFI, you need to:
- make sure the thermostat washers are clean
- the car runs between 3 - 6.5% (idle to 2500 rpm - a little higher CO won't hurt)
- make sure your fuel system is clean - mine was pretty clogged up, and the engine was carboned from running the wrong exhaust system

Try BS Autosport - Nigel Bainbridge - an expert with the 2.7 MFI cars.
http://www.bsmotorsport.co.uk/

Best
Dom

[mallen282]

Thanks guys for all you're advice.

I've changed the Plugs, Leads and Distributor Cap to date and this has seemingly had a significant benefit although it's still hesitating slightly around 2000-2500RPM!!!

I'm hopefully going to change/renew the points next weekend and re-adjust the the Mixture & CO to 3-4% 'ish so fingers crossed this should eliminate the problem....

Rgds

[domtoni]

Mark,

Should have noted before. Try doing a search on Pelican Parts for MFI issues. There is lots of stuff. Try to understand the problem before undertaking any serious work.

Further thoughts:
- the pump has two racks. The lower rack has the thermostat washers, and controls idle up to about 2500 rpm
- the pump moves from the lower to the higher (high speed) between 2500 and 3500 rpm
- cross over can be tricky, so you may get some bucking there
- the pump has a start solenoid, which dumps fuel into the engine when cold
- the pump has an overrun solenoid that shuts off the fuel flow into the pump when the engine is coming down in rpm
- your emissions should be between 3 - 6.5%, higher is OK, but 8% is the max of OK

Further words of experience:
- make sure the electrics, points, plugs, valves are all in order before undertaking any MFI work

Best
Dom

[domtoni]

Mark,

3% at idle
6.5% at 2500 rpm
is the recommended fuel CO emissions

Dom

[tanick]

Not near Cambridge, but not too far either, JZ Machtech (M25 nr Jn 20)overhauled my MFI this week. Pulls like a train now and starts right on the button (something its never done before).

[mallen282]

Nick,

Can you give me an idea of what an overhaul incorporates and what they charged you

Rgds

[tanick]

I've PM'd you.

[domtoni]

Mark,

One other thought. If you want to go down the route of overhauling the pump, try Nottingham Diesel. Sorry don't have the number handy. My local Bosch Agent gave me their name.

Best
Dom

[mallen282]

Thanks to Dave for the Porsche check,adjust manual....

Many many thanks to keith for helping / doing the Timing etc this evening..

HOWEVER She's now running like an absolute bitch with a headache.......despite the Timing and Dwell angle having been adjusted as per the manual (With new Points fitted) tonight

We had to move the distributor a fair amount to get the timing etc correct (almost half the adjustment slot!) and we've double checked it all, so the timing and dwell angle are correct....She pulls like a train above 2000rpm and at any time when the throttle is flat to the floor...but she kangaroos violently when feathering the throttle and now will not tick over.....

I'm going get the fuel pressure and flow checked next but do you guys have any better idea's???

Thanks

M.

[domtoni]

Mark,

Did anyone ever reset the fuel mixture so that it reads 3 - 6.5% between idle and 2500 rpm?

thanks
Dom

[domtoni]

Mark,

SHould have said this as well. Presumably you mean the car is bucking. That is usually the indication of a lean condition (as I found). The bucking is caused by the cross over between the low and the high speed fueling.

Dom