It's the MFI pump!

[Matt Holcomb]

If you haven't read my Rob Roy report, then you won't know what I'm talking about.

Rob Roy Hillclimb -- Part One

Basically, my engine won't rev past 4,000rpm under load. My mechanic thought it was the ignition system. On Saturday he tried a new coil and another CDI unit. He checked all the wires -- everything related to the ignition system.

He called me at 10:00AM this morning to tell me he was now 90% sure it was the immobiliser. But to be 100% sure, he was going to fabricate a new ignition system that bypasses the one in my car.

At 3PM I received another call from John. This second ignition system didn't do what he thought it was going to do. It's not the immobiliser. It's not the ignition system. It's the MFI pump -- it's jammed, and it needs to be taken off and examined.

Even if it can be fixed without being rebuilt, I'd be crazy not to have the pump rebuilt.

But I was crazy to expect that it would be something other than the MFI pump! No, I've just had the engine and the transmission completely rebuilt, it couldn't possibly be the next most vital component! No way!

*Sigh*

Before I get used to the idea of spending $2,500+ on my pump, does this sound plausible?


Matt Holcomb
MFIWDP
1974 911 Carrera 2.7 RoW
1975 Mercedes-Benz 280SE
Dedicated Homepage
Engine Rebuild Homepage
Porsche Owners Gallery Profile
Pelican Gallery Profile

[Adam]

Matt,

Your first call should be to Injectronics Pty Ltd in Dandenong.

They're mechanical & electical fuel injection specialists. They do wonderful work on a changeover basis. Give them a call, I don't have their number handy, but you'd be remiss to not give them the opportunity.

I'll call you tomorrow, man.

btw, Our mechanic just called. Looks like we've dodged the bullet on the 3.2!

[beepbeep]

*cough cough*

Yeah, i know you're MFI-nut but 2500$ will give you programmable electronic EFI plus ignition that will perform better than any MFI in existance.

And don't tell me MFI gives better responce... :-)

You are aussie, right? Get yourself one of those Autronic-kits with MAP-sensor and direct ignition. You can get rid off both ignition dizzy and all MFI-crapola...it's a pity you didn't opt for dual-plugging your heads when you had them out...

Using Autronic EFI, you can program all ignition and fuel curves at will, you can even add lambda-sensor for closed-loop control and even use data logging to see what happened.

Dual plug + EFI + direct ignition + closed-loop lambda = less preignition = more power!

[HawgRyder]

I just read the circumstances of the problem.
It sounds more like a jump in timing to me.
Is it possible the one of the cams has jumped a tooth?
Does the engine rev freely to 4000? or...does it slowly get there?
If it is slow on the revs...look to the cam timing.
Hope this helps.
Bob

[Sean Hamilton]

Originally posted by beepbeep
Get yourself one of those Autronic-kits with MAP-sensor and direct ignition. You can get rid off both ignition dizzy and all MFI-crapola...it's a pity you didn't opt for dual-plugging your heads when you had them out...

Ah "hindsight" a vision splendid. Indeed, I'll save this as future "insight"

Matt:
"Before I get used to the idea of spending $2,500+ on my pump, does this sound plausible?"
Crikey $2.5K. Can John temporally swap over the pump for another, to confirm the diagnoses?

Adam:
"btw, Our mechanic just called. Looks like we've dodged the bullet on the 3.2!"
Tell me, tell me. Don't hold out.

[Adam]

Ok,

Sorry for crashing your thread, Matt...

Our mech has called. He'd started by looking over the engine bay, for things out of place and discovered a couple of interesting items where they weren't supposed to be...

1) Decklid light (internal) had fallen apart and part of it(apparently it's metal) had become wedged under the main pulley causing the screeching/thrashing sound. He pulled it out and the noise stopped.

2) The heavy knocking sound (which came and went very quickly when it happened) looks like it's the Alternator. He told me over the phone that the voltage regulator was the culprit. After disconnecting it, the motion of the fan etc is perfect. When it was connected, the fan makes a slight clunk/knocking sound. Once it's replaced, all noises will be gone. He tells me that when the alternator fails, they make all kinds of interesting noises.

So, the engine bay inspection light is fixed, the alternator is out and being overhauled today and we should be ok. He is still going to perform a leakdown/compression test, but in his opinion, everything's going to be fine. The 3.2 is running perfectly smooth, as it has since we got it. Despite all the expensive sounding noises, it's never been running rough.

I'll know more this afternoon, but I'll keep you guys posted.

[Todd Simpson]

Matt-Here's a rare possibility. I just installed a 2.2S motor in my '71T. Started and idled beatifully, ran great around town but would only pull 5K in 1st, 4K in 2nd, 3500 in 3rd, etc. Top speed was 75 mph. Spent a day with a bunch of help tracking it down, 2 of the fuel lines on the fuel filter were reversed. The engine was getting enough fuel for small loads but not enough when you really got on it. Fixed the lines and ZING, right up to 7K and beyond like it was supposed to!

Doubtful this is your problem, but worth a shot. Test the fuel delivery both before and after your fuel filter and see what you get.

Todd

[Matt Holcomb]

Beepbeep,

Man, I admire your persistence, but as far as I'm concerned, I'm driving a piece of automotive history that is still able to dish out a bit of punishment. The simplicity of the MFI system is breathtaking, as its performance. Sure, it's not as malleable as EFI, but I don't have $6-8K, which my mechanic tells me a complete EFI conversion will cost!

Bob,

It revs fairly freely to 4,000rpm under load. When stationary and in neutral, it will rev beyond 4,000rpm, albeit with a bit of reluctance.

Sean,

John un-jammed the pump, but after a minute or so, it jammed up again. He thinks it's a governor cam spring -- the pump needs to be opened up.

$2,500 is the very least it will cost to get it rebuilt. Realistically, I'm probably going to have to shell out close to $4K! John has a used replacement pump, but to buy it off him I'd have to find $10K! Insane, I know.

Todd,

My mechanic has checked everything; the pump was the very last thing he wanted to check as he wants me to avoid spending $2,500-4,000 as much as I do.

But thanks for the suggestion.


Matt Holcomb
MFIWDP
1974 911 Carrera 2.7 RoW
1975 Mercedes-Benz 280SE
Dedicated Homepage
Engine Rebuild Homepage
Porsche Owners Gallery Profile
Pelican Gallery Profile

[emcon5]

We are talking AU dollars, right? That is about $1400US, so still spendy, but not into the "prison sex" area yet.

Tom.

[jkeyzer]

Matt, you have a 2.7 with MFI... Don't change a thing. (But if you do, I'd take that engine in a second.) Bite the bullet and have the pump rebuilt. $1400 USD is probably about right, although Gus at Pacific Fuel Injection quoted me a bit less when I talked to him. You might be able to find a cheap used pump (like a 2.4T) for parts and that may bring the cost of the rebuild or repair down quite a bit.

You might want to have the injectors checked out and make sure the belt on the pump isn't slipping and the pulleys are in good shape before taking the plunge.

[Weapon Of Choice]

Matt,
that is so sad to hear, i still remember when crom was getting the rebuild when we went down to john's work shop and he spoke about the fuel pump.

by all appearances it seemed ok, but i also remember us getting scared about the pump breaking down, being that it is so complex and so expensive.

i hope that it will not cost to much it has been a very expensive year for crom this year

there might be some creedence in the efi substitute for the fuel pump. you might wanna call where adam said and they might have some alternatives that might not break the wallet so much

i know you are trying to keep the car as original as possible but there are always alternatives that might be worth a look at.
i hope it all goes well buddy and keep us posted

[CamB]

EFI can be cheap....

... but not that cheap. Conversion of the MFI stacks to EFI (injectors, fuel rail, etc) would be dollar consuming.

Then there is the computer and about a zillion sensors and plugs. Finally a few hours on the dyno.

I can't see A$4k. I also don't see A$8k.

Either way - bummer Matt!!!!! Paying for that rebuild will be no fun... can you get John to somehow verify it is the pump (ie swap in his good one).

[beepbeep]

Sorry, i assumed he was talking US$ ...

Anyway, EFI isn't so expensive as one might think. Second hand SDS-computer can be obtained pretty cheap, and his 2.7 N/A engine doesn't need huge injectors that turbocharged would. I don't know so much about 2.7 engines, but one could probably use complete intake and fuel-rails (toghether with injectors) off a 84> Carrera ...

There are not so many sensors, only MAP, Hall-sensor on a crank, throttle potentiometer, temperature sensor and lambda-sensor (if you opt to use closed-loop).

You can map such vehicle on the road using wide-band lambda and laptop.

I'm not trying to bash MFI or anything, i just feel sorry for guys expiriencing costly malfunctions of outdated equipment that can be replaced by modern, cheaper and better-performing system.

Check out:
http://www.sdsefi.com/

[CamB]

I agree - second hand bits would pull it down a lot, as would:

"one could probably use complete intake and fuel-rails (toghether with injectors) off a 84> Carrera ... "

But that is BLASPHEMY!!!!! You gotta leave the multiple throttle bodies!!!

On the sensors, I probably over emphasised, but by way of example, my engine has (technically will have):

throttle position sensor (TPS) ($???)
Air pressure sensor (US$55)
Air pressure sensor terminal kit (US$10)
Air temp sensor (US$40)
Oil temp sensor (US$15)
Special plug for injectors (US$30)
Special relay for ??? (can't remember) (US$25)

I mean that is ~US$175 + TPS... (and plus taxes)

Actually, I remember where it hurt - I just looked at the invoice again - 2x Bosch ignition modules and coils ~US$450 ish. Bugger.

And installation - plenty of custom work and stuffing around. If you do your own labour, then it changes the calcs a lot though... but when you see it on the engine and the engine bay console, it starts to look pretty complex. Throttle position sensor is on right of linkages. The injector plug in all its US$30 glory is the small grey plug sticking out to the left.

[Sean Hamilton]

Wow. I'm gob-smacked

Appears that's there's more to that engine than meets the layman's eye
I'm a complete novice with this so excuse my dumb questions
What's with the two distributors?
Where will the extra plug leads go?
Is this, as they say "twin plugging"?

I better stop now

[beepbeep]

CamB:

Yeah, but in this case he wouldn't use those double iginion dizzy's at all!

That's the beauty of direct ignition, there are no distributors, it's ECU that controls ignition, advance etc.

Sean: Yes, it's so called "twin plug" -installation.

There are no problems with using multiple throttle-bodies. I mentioned using second hand Carrera manifold as a way of keeping it cheap. Actually, i think it should be fairly easy to bodify existing MFI-injector holes on intake stacks to accept electronic injectors.


Here's SDS installation on SC-engine with multiple throttle-bodies:

Notice absence of ignition distributor. This engine was dynoed @ 254 wheel HP... (should be around 300 crank HP)

In direct-fire setup, every spark-plug has it's own ignition coil that is controlled by computer. Same sensor that controls fuel-injection timing is used to control ignition timing as well.

If you are handy, shop around and are able to do some work by yourself, it's possible to do EFI conversion surprisingly cheap.

New SDS-EFI, all sensors and six injectors cost around 1400$...go figure.

Of course, one could always save MFI-pump and convert it back to original state. No offend, Matt's car is beautifull, but it's not 73' RS that has to be kept original to the last bolt to keep it's value.

Cheers!

[beepbeep]

Here's dizzy-less installation on dual-plugged turbo engine:

[CamB]

Yep - it is twin plug. In this instance a 964 distributor has had an SC crank gear attached (I think). It has a chopper plate inside to provide a trigger for an older MoTeC computer, which directs fuel as well to modified MFI throttle bodies.

Twin plug is needed to allow higher compression (10.3:1 in my case) with pump gas (I'll use 98 RON).

Yes - direct fire is better again (no distributor) but needs a crank trigger assuming the distributor is ditched. Seemingly simple stuff like that gets very expensive quickly (again!) when you get prices like Clewett Engineering quotes ($400ish). For direct fire - I assume you then need multiple coil packs (like electromotive?????).

In Matt's instance, it would probably be cheaper to use his distributor. I agree, if you are handy there are secondhand parts which would make this MUCH cheaper. But you have to be handy to save the labour.

Now, I have to make an important disclosure here. I am saying what I have either researched or been told. I am paying someone to do the stuff to the engine (waaaaaaaaah I am NOT saving the labour, although I am not paying for R&D - he has done it before and I bought the engine semi-complete).

I don't have the time (or the gumption) to do it myself. Therefore, I may be wrong, and if it seems I am - let me know!

[Matt Smith]

Matt: why don't you just open up the pump and check the governer spring. Replace if needed?????

Removal/replacement of the pump is childs play. Open up a couple of inspection hatches on the pump and voila: reattatch the spring? Whatever, it can't be that hard. Plenty of exploded diagrams to work from here on Pelican.

It never fails to amaze me how scared of this pump everyone seems to be. Why would you be crazy if you didn't fully rebuild it?

Cam: that motor is pornography.

[Matt Holcomb]

Guys,

I might convert to EFI with the next tear down. I think to do the EFI conversion justice I need to have twin-plug heads. Yes, definitely.

Goran, that SDS SC engine is a work of art; those throttle-bodies are very sexy indeed!

Cam's engine ... Brilliant. This is what happens when you ask questions. Cam, I can't wait for your first impressions!

And Matt, I'm actually quite tempted to have a go at repairing the pump myself! As Adam Chaplin said yesterday when I told him I was tempted to have a go at it, "What's the worst that can happen? If you can't fix it, at least you'll have disassembled it for someone like Gus Pfister."

Weapon of Choice is absolutely correct: it's been a very expensive year for 'Crom.' I could have purchased a scruffy 2.7 with the money I've invested. And that's what this is, an investment. It's not a '73 RS, I know, but as Keith Seume will tell you, RoW Carrera 2.7s are now collector's items -- only 3,000 were made, and now people are starting to realise that these cars actually offer a more rewarding driving experience than the RS Touring, despite the impact bumpers!

Having said that, I am a fan of MFI. I know what it's like to race a car with this much vaunted injection system. It's not a preference that's based on theory. It does what EFI can do, and it's simpler. It's mechanical, by god!

Below is from an e-mail I received today from Jeff Phillips:

"I was at a track in Ohio and the car ran great for the first day and a half. Super strong, pulling away from 993's and even keeping pace with a couple of older turbos. It is fun to surprise those guys with their fancy cars thinking that this little '74 hasn't got anything then blowing by them! It doesn't seem that there are a great number of people over here that understand what the Euro Carrera is. Even after you tell them it is a Euro they still have that confused look on their face. Once you mention the '73 RS engine they think that it is an upgrade and not original. I will never discredit a true '73 RS but it sure is fun to have the "sleeper" '74 to run with those unsuspecting drivers!"

MFI is the reason why Jeff's Carrera is able to pull away from 993s and keep pace with older 930s. It's thirty-year-old technology and it's still more than competitive. I really dig that. At the moment, I just happen to dig that more than EFI.

But hey, I now cry for no real reason. Apparently it's a mid-20s thing.


Matt Holcomb
MFIWDP
1974 911 Carrera 2.7 RoW
1975 Mercedes-Benz 280SE
Dedicated Homepage
Engine Rebuild Homepage
Porsche Owners Gallery Profile
Pelican Gallery Profile