MFI Experts! Need Guru help....

[Tspringer]

I have posted some on this problem before.... see these posts for lots of detail:

Gasoline in the oil ! Help !

Fuel in oil.... followup


Basically I am getting lots of fuel dumped into the oil on my 2.7RS MFI engine. Internation Performance in Roswell GA has worked on the car for the last 3 weeks. I have also spoken with Gus at Pacific Fuel Injection a couple of times at length about the problem.

IP tested both the cold start solenoid and the cold running thermostat. Neither of these is leaking or putting any fuel into the intake when the car is not running or when they are not supposed to. It does not appear these are the problem.

Gus does not believe its possible for an internal pump leak to result in so much fuel getting into the oil that it causes the oil level to rise and be forced out the breather. Also, this pump was rebuilt only a few years ago.

This leaves the injectors. IP does not have any means of testing the injectors. I am currently searching for someone in Atlanta who can test them.... or someone is a REAL MFI GOD in Atlanta who I can take the car too.

I am thinking one or more of the injectors is allowing fuel to flow past all the time including when the car is sitting (not running). This car runs great. Tons of power. Only the tiniest amount of rich running black smoke on application of hard throttle.... in other words just like good MFI should. It does not foul plugs. There are no running issues at all.

If anything was causing the car to run so rich that raw fuel was unable to all be burned and was running past the rings.... would not the car be throwing clouds of black smoke and fouling the plugs?

This is really getting to be a mess. Im now facing a process of elimination that could quite easily result in $2K + new injectors, rebuilt pump, etc and the result could be the problem remains. Nobody can identify what is causing this.

I do not want to switch to carbs. I love the way the MFI works and sounds.... but I may end up with no choice. The MFI appears impossible to repair.

[john walker's workshop]

how about sending the injectors to gus. is the pump timing set at the FE mark after #4 TDC, or after #1 TDC? should be after #4 so the valve is open to take the fuel in.

[tryan]

yes,you could have an injector dribbling? rich , richer, richest. pulled the plugs to check for offending cylinders? got to love mfi.

instead of paying the labor to check my injectors, i just replaced them. i paid about 60 per. shop around.

you might look into the cold start system. the residual pressure may be allowing a small amount of fuel to flow all the time, but filling the crankcase with gas would have me baffled/frustrated/confused also.

[silverc4s]

If it is still hooked up, I'd disconnect the fuel lines to the cold start system, it's a damn fire hazard anyway. I just do without. Only hard to start when it's been sitting too, too long...;-)

That could well be your problem - not too many sources for that much fuel...I doubt it's an injector, it would run badly too then, I think..

ADDITION. I just thought about it some more. Even if an injector opened at a MUCH lower pressure (like 100 psi instead of the 225 or so of a normal), it could not possibly source that much fuel through the MFI pump, IMO.

[Early_S_Man]

Terry,

I agree with Bill that the cold-start solenoid should be disconnected uintil this fuel dillution issue is resolved!

The quantity of fuel available for injection is fixed by the pump, PERIOD! If an injector opens at a low pressure, the atomization and pattrern won't be optimal, so, it could be drops of liquid fuel rather than a spray mist, and the result would be more fuel in the oil than normal ... the cylinder 'wash-down' effect.

After three weeks of work ... what are the CO numbers?

Sounds to me like a new shop is needed ...

Or, get a Gunston Gas Tester ... and do the work yourself ...

[Mr Beau]

First off, the basics: how does the car run, and what do the spark plugs look like, are you sure fuel is in the oil? If the thing runs great and the plugs look normal, the fuel likely isn't entering by the normal means.

If the plugs are black, then it would appear it's running too rich for some reason, and that's how the fuel is entering. If that's the case, you can start narrowing down the various items that would cause it to run rich.

Does you every have to crank for extended periods of time to get it to start? That would be the most common scenario of diluting oil.

Hope this helps!

Matt
'73 911E

[jeff m]

The car runs well!
Therefore it is very unlikely to be a delivery problem, injecters opening low etc
The only place I can imagine it could be is fuel from the pump at fuel pump pressure entering the oil side of injection pump running down that pipe with the oil back to the sump.
You could remove that hose, put it into a container run the fuel pump (ignition on) and see if you get fuel. You could also try it with the engine running for a short time. (looking for fuel oil mix)
This seems such an obvious test I'm sure the shop would have already done it, but I thought I'd post it as it may help.
Jeff

[Tspringer]

Jeff M. They say they did that test and it showed no problem. I may do it again myself.

The cold start system was supposedly tested and is not putting out fuel when its not supposed too. I may test this some more myself by hooking it up to a bottle and driving around. Also going to see if there could be some sort of short somewhere that is intermittent.

Matt, the car runs great, no fouled plugs, no abnormal black smoke. If it was running so rich that the excess fuel could not be burned and was diluting the oil to the point of filling the crankcase.... I would expect clouds of black smoke.

I dont know the CO numbers. Surprisingly they have not done that test though I did ask them too today. Well see....

I will probably be bringing the car back home and digging into it myself. I will probably end up sending the injectors and pump out to be rebuilt. The pump was rebuilt only 2 years ago...

It seems the only way to diagnose and repair MFI is to basically replace everything and hope for the best.

Terry

[jeff m]

The hydrocarbons in conjunction with the co will give you a very good idea what is happening.
If you are getting that amount of fuel in your oil by the injector route your hydrocarbons will be off the scale of the tester through the exhaust. (even a misfire on one cylinder shoots um up)
If they are not, then it's the seal in the pump between fuel and oil.
I don't think that would be that expensive, damn inconvenient, but not requiring a rebuild as is generally understood.
I am also curious how the shop is ruling out each item. Are they constantly changing the oil.
One other thing worth checking yourself is that the thermotime switch and the relay (no 12 I think) have not been rewired with a battery from a new source. Both of these are wired from the starter sol (yellow wire)
and are only live during starter op. I know the cold start sol is disconnected at present, but I have read a lot of posts of people hot wiring them them with 12v. A safer hotwire would be a ground to coil of relay 12 and still use the solonoid 12v so relay 12 can op cold start sol.
The pressing of that switch or button (by a child) or sticking contacts of a 12v hotwire would certainly dump large unwanted amounts of fuel!
But I assume your car is untampered with.
Failing that, drive the car to Oregon or Seattle!
Good luck
Jeff