BIB5566

[knapmann]

Hmm just went for a drive, all the same issues, pulled onto my drive with engine idle at >2k again after dropping too low and stalling a few times before that. Looked at my fuel pressure and it was up at 16psi. Took the regulator fitting back out, gave it a spray and some actuating refitted it, now its at 5psi! When it was sitting at 10.5psi this morning! Getting miffed off with this now. I could do with a new regulator fitting, one I know works perfect but they are crazy money for a little fitting.

I dont think 69 cars had the access holes, and i thought the push and turn only applied to the lower idle adjustment, not the main rack adjustment or am I wrong?

Thanks for the help!

Neil

[knapmann]

No wonder I cant adjust it. I just looked inside by taking the side cover off the pump and there is a lever arm right in the way of the main rack adjusting screw. This lever arm pushes the end of the rack on the screw and totally blocks access to it. I cannot see how one is supposed to adjust the rack with this lever arm right in the way.

I *think* its a lever arm from the additional cold start solenoid only found on 69 pumps, I *think* when activated it pushes the rack to enrichen the fueling, in any case it appears to make adjustment impossible?

[Cortina]

Got to be a way of adjusting - Porsche would not have designed it like that. Is it time to look at official workshop manual or should we wait for someone with 69 pump knowledge / experience to come along ???

[knapmann]

Got to be a way of adjusting - Porsche would not have designed it like that. Is it time to look at official workshop manual or should we wait for someone with 69 pump knowledge / experience to come along ???

Just got the answer from someone on Pelican, if only I had known this 5 hours ago!

"There is a bolt on the left of the pump. You loosen it, backing it out about 5-6mm. This moves the arm away from the main rack so you can make an adjustment. Tighten the bolt back up when you are done."

[knapmann]

Naturally this bolt, like everything to do with MFI is a total bitch to get at, but having done so I put 3x ccw clicks on the rack went for a drive and all my hesitation at 3-4k rpm has gone! Yay! A really frustrating day but I dont mind that when there is some success at the end. I will turn it back a click before my next run and see how it performs then.

I will have to apologise to the engineers of yesteryear. If I knew about the lever arm issue beforehand, the adjustment difficulty would have been downgraded from "basically impossible" to merely "a pain in the arse". Its a shame I have seen no mention of this problem on all the dozens of MFI pump adjustment articles and threads I have read over the last few months.

Ill take my pressure release valve to work and ultrasonic clean it in injector cleaner tomorrow. Ive not given up on it yet. My idle issue seems to be worse now I adjusted the pump. Am I right in thinking adjusting the main rack will throw out the idle mixture also? i.e the engine will need re-correlating after every pump adjustment. Its a shame as other than my idle issue the car is amazingly powerful. I still cant believe its a 2.0l A high compression 2.7 or 3.0 in one of these must be a total monster.


Im not sure how long my 1st gear will last with all of the crunching into it i have to do. The bite point is high on the pedal and the pedal is not bottoming out and hitting the pedal board, its stopping because the clutch wont go any further (Its adjusted to the max at the transmission end). No other gears are affected so I cannot see it being a clutch issue. It also pops out of 1st gear which is annoying as then you have to crunch it back in again this and the idle being stupidly high or stalling altogether means everytime i have to stop at a junction or to turn right or at lights im worrying about getting it into gear, keep the engine going, then when it dies trying to get it started again. It basically means I cant really go anywhere properly in the car as of yet. Im starting to get the hang of the 2nd through 5th shifts though.

I also have a good sized oil leak on my engine. Not sure where its coming from Im sure they are a total old git to try and source. I know these engines leak oil but mine is excessive. I know the rocker cover on one side is leaking and thats an easy fix but the main leak is dripping off the middle of the engine casing so its not coming from the rockers. Its also not from the sump cover as I freshly changed the gaskets and rtv'd that all together a few months ago. I really hope its not something id have to take the engine out to fix....

[Cortina]

Idle mixture - not so sure. Quick sniff at the manual shows some form of idle adjustment screw / ? at the bottom of the pump (also at the back) ... ?? in the middle of a round shaped assy of some sort ... what's that for ?? Maybe worth finding out ! Idle fueling circuits are usually "different" to main mixture control.

[hot66]

Main rack adjustment does change the idle mixture too

[knapmann]

I thought I had read that somewhere. I think I will turn it a click back then try and recorrelate. I dont think that the mixture setting is the idle issue though. Its something more inconsistent something which is high one minute then low the next... which is why I think advance and fuel pressure/flow are likely to be the main culprits.

[hot66]

I think you look at the main rack as the overall mixture setting, then fine tune idle and transition with the idle screw

[knapmann]

Yes this was my understanding, i still have work to do but making progress all the time I hope!

[knapmann]

I think I've cracked it!

Having solved my mid range hesitation last weekend I was left with the idle problem. A few things happened last weekend that got me thinking this week. There were two instances where I left the car idling at 1000rpm for 30seconds and suddenly over the space of 10 seconds the idle went up to 2500rpm by itself. Now I had been thinking my idle issues were distributor related but this made me think that it cant be, if its idling happily at 1000 the timing wouldn't just change magically by itself to raise the idle.

I knew the issues wasn't an air leak as it would cause the engine to run crap throughout the revs, which it wasn't doing.

It must be a change in the fueling by the MFI pump for some reason. As I know the pump is returning to home I knew that the throttle mechanism wasn't causing an issue. My first port of call was the fuel pressure as I still hadn't bottomed this issue. I ultrasonic cleaned the return line valve at work but it was still giving erratic pressures. There was nothing more I could do with this valve than prise it open and try and look inside it to sort it out, with the hope of being able to put it back together. If not id be forking out £150 for a new one. I couldn't find any reference to anyone opening one of these up before so I just winged it.

I prised the crimp open, to find a brass ring, a nylon? square and a spring. Its the nylon fitting that does the sticking. Its square and only the corners touch the inside bore of the fitting itself. What I was finding was that it was a tight fit inside the fitting for some reason I cannot fathom. It would stick open or shut despite all my cleaning efforts. So I went at it on the corners with a bit of 400 grit to take a fraction of a mm off each to have loose, but not too loose fit in the bore. Put it back together, press the crimp back over and jobs a gud'un. My fuel pressure has been rock steady 9.5psi since.





That's not to say the issue was fixed. My idle was still all over the place. So back to the drawing board. What else effects the MFI pump fueling? The barometric cell and the thermostat. Now I haven't touched either of these to date as all the advice you tend to hear is "don't touch the MFI pump", but i thought Id start looking into testing these. I started with the thermostat, I took it apart and cleaned it all out, but it looked pretty clean already. The heat exchanger hose was in good nick and clear of blockages. I read that to test the thermostat one should get the engine to full temp, then check it is fully actuated under the access cover on the pump. So I drove around for 30 mins pulled back onto my drive with a 2500rpm idle again, checked the actuation and it was way off, like 5mm of travel still to go even though the engine was at temp.

Now my thermostat has been modded at some point with a screw in the cap to make adjustment easier. So I screwed it in to fully actuate the thermostat and lean out the MFI pump, as I did so the idle dropped right down to 900rpm. Hallelujah! But now I'm thinking my pump is running way leaner than it has been so far... another spin around the block and yes. my idle is ok but the normal running has gone to shite now. Its gonna need a decent number of main rack clicks to richen it up to make up for the thermostat adjustment.

3 clicks, drive... 3 clicks, drive... 3 clicks, drive... 3 clicks, drive... 3 clicks, drive... 3 clicks, drive... yes 18 clicks of the main rack and it was finally there. Took all afternoon at 20mins per adjustment. I have an engine that idles rock solid at 900rpm, and pulls through the revs without hesitation! So good to finally have an engine that runs properly! I drove around for an hour just enjoying watching the rev counter drop to a steady 900 every time I came to a stop. I'm sure there is room for more fine tuning and improvement but i'm really happy with what I have achieved so far all of which without throwing loads of money at it (very tempting to just chuck it in a garage and say "fix that"). I've also learned so much about MFI in a short time. The most important thing I've learned is to listen to exactly what the engine is doing, and to use your knowledge of the system to think "what could make it do that" and "what couldn't make it do that"

And how good is MFI when its running properly! OMG its amazing!

[Jonny Hart]

That's great news! Enjoy for now and continue the shakedown but then it is well worth revisiting a bump in the advance map.

[Gary71]

Brilliant.
Really good to see logical step by step problem solving and learning getting it fixed.

Unfortunately I don’t think the garage exists that are prepared to put this much time (and more importantly the hours of thinking) into this type of thing to really get to the bottom of this.

You are now the expert!

[IanM]

[Lightweight_911]

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An excellent result !!

It just shows what a logical mind combined with a refusal to accept defeat & a 'what's the worst that can happen ?' approach can achieve ... well done !!

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