MFI Starting woe's

thevojtiseks · 04:55 PM

Help !

I have just got my engine all rebuilt and back in the car - it's not run for many years - and I can't get the car started. I have spark, but I started looking for fuel and there is nothing at the injector....I checked for fuel at the inlet to the MFI pump and there seems to be good flow. I removed No6 injector pipe to check for flow to each cylinder and there is nothing when I'm cranking....I have cleaned all the pipes prior to reasembly, so I don't think the pipe is blocked, and the pump was rebuilt.....Any ideas ?? is there a pump priming proceedure I don't know about ?? Thanks very much

1971 911s, 2.2 MFI

Jay Auskin · 06-17-2004, 07:11 PM

I sent my injectors out for cleaning and it was teh best money ever spent. I had all 6 injectors ultrasonically cleaned and flow tested for less than the cost of one new injector. You'll want to contact a diesel injection place because the gasoline guys usually can't test at high enough pressure. I used Midwest Fuel Injection in Orland Park, IL.
http://www.mwfi.com

thevojtiseks · 06-17-2004, 07:21 PM

Thanks for the tip Jay - I forgot to mention I bought 6 new injectors also (Mine were beyond repair). I disconnected No 6 injector between the pipe and the injector, thinking that without the injector I should see some fuel...Nothing.....

Henry Schmidt · Henry Schmidt's Garage

It is not uncommon for the piston in an MFI pump to stick after a long vacation on the shelf. If you feel ambitious, pull the side covers off the pump, and turn the pump by hand. If you see the springs that control the pistons compress and expand while you turn the pump, then the pistons are not stuck. If they are stuck, send it out for repair or spray with carb cleaner until they free up. If you choose this method make certain you get all the card spray out of the pump before reinstalling the pump.
If your still not sure, give me a call.

thevojtiseks · 06-18-2004, 07:46 PM

O.K. I took the side cover off and it looks like the springs are compressing. I also checked the rack and this moves and returns freely. After cranking for a while If got a few drips out of the end of the injector pipe to No 6 cyl - not very much, but perhaps this is correct ???

How much cranking do you typically have to give a car with a rebuilt pump and new injectors ??

Thanks

Eagledriver · 06-18-2004, 09:10 PM

I was suprised by how much cranking it took with my engine. I was sure something else was wrong and did all kinds of trouble shooting like you are doing. I would say it took at least one full minute (maybe up to 2 min) of cranking total to get the car to fire. Of course you don't want to do the cranking all at once so as to not overheat the starter.

-Andy

dtw · 06-18-2004, 09:43 PM

Another very recent thread with similar issues noted that there is very little fuel coming out at when cranking the engine over. Sounds like if you have clear lines, free pump pistons (did you check both sides??), and new injectors, fuel isn't the issue. Is cold start circuit functioning? Are you using the hand throttle or holding the throttles open a bit while cranking? Have you gone through CMA? Have you checked the pump sprocket relative to engine position? (I believe 40 degrees past TDC on #4 cylinder, but don't quote me).

I may get taken to task with this, but on the last couple engines I've started for the first time, I've had a buddy cranking the ignition while I fire a few quick bursts of carb cleaner into the intake stacks. It seems to have helped get the engine started on those "first starts" until the ignition timing and mixture can be fine tuned.

Henry Schmidt · Henry Schmidt's Garage

Even without priming the pump, an MFI engine should start on the cold start injectors. If it doesn't want to start at all, try starter fluid.
Be careful. That stuff will light you on fire if the car back fires and you're close by.
You'll be doing a Richard Pryor impersonation if things go wrong and I wouldn't want that.

Shuie · 06-19-2004, 11:00 AM

Quote:

Originally posted by Henry Schmidt
Even without priming the pump, an MFI engine should start on the cold start injectors.

Thats what I was thinking. If a MFI engine is hard to start when its cold, then the cold start system is either dsiabled or not functioning properly. Your cold start system may be disabled or non functional. Check this thread out.

Im not real familiar with MFI outside of my '72 2.4 motor. I don't remember if in '71 the CS injectors were in the airbox or not. If they are, your CS system needs to stay disabled (bad fire hazard, no joke). Be very cautious and aware of the old and brittle fuel lines. Make sure everything is in place and in good shape. If the lines are old, start planning on replacing them.

good luck!

thevojtiseks · 06-19-2004, 04:53 PM

The good news it it's running now !! Took the advice on a bit of cold start help and after a few tries it started to fire. It' took a couple more goes as the fuel pressure built up, but eventually it was running and able to restart on it's own - Whey !!! Along the way I've discovered the cold start system is not working....So that's one of my next projects...I did notice some fuel leakage from around the injectors, after tightening the fuel line a little more this seems to have fixed itself in all but one line, which I may end up having to replace unless I can re-flare the end...

Thanks for all the advice, this has been a great help !!