Way too much gas, 73 1.7 with FI Options

[EJP914]

hello!
Looking for some ideas on why the spark plug electrodes are wet with gas after running the car for only about 20-30 seconds. Something is causing way too much fuel into the engine. Car starts at the turn of the key, but stumbles and runs rough. Exhaust smells like gasoline.

I have checked, replaced, or installed known good parts.
New plugs, points, condenser.
Cleaned trigger contacts. Distributer other wise works as it should.
Swapped in known good relay board and relays
Swapped in known good ECU.
Installed new fuel injectors, Standard Mfg type.
Fuel line pressure at 25 lbs.
Swapped in “adjusted” MPS. (Maybe still too rich?)
Timing is good but not spot on.

I have not yet checked CHT sensor or cold start valve (may be stuck open?). Not sure what else to check? I have never seen this much gas get pumped into an engine.
I would very much appreciate any advice and/or guidance. Thanks.

EJP914

[FlacaProductions]

I'd check the cold start valve.

[brant]

CHT and mps failure both cause excessive rich conditions

[JamesM]

Swapped in “adjusted” MPS. (Maybe still too rich?)

I have not yet checked CHT sensor or cold start valve (may be stuck open?).

Those are the three, but im leaning towards the MPS.


For the cold start valve to be stuck open it would first have to open which takes either very cold temps, or a grounded out wire to TS1. Quick test, you could try unplugging the injector but I doubt that is your issue.

CHT failures usually result in a no run condition. Rich to the point of having to floor it to keep it idling.

[emerygt350]

Check you cht just in case. Easy peasy. Then check your mps. I am betting it doesn't hold vacuum.

[burton73]

I don't know why your car is pumping too much fuel but, I want to point out that you definitely need to change your oil or you can spin a bearing. I did that in a MFI 911 way back when I was 27

Best Bob B

[emerygt350]

I don't know why your car is pumping too much fuel but, I want to point out that you definitely need to change your oil or you can spin a bearing. I did that in a MFI 911 way back when I was 27

Best Bob B

Yeah. Check your oil... It may be mostly gas.

[wonkipop]

another possibility. fuel pressure regulator diaphram failure.
can leak fuel back down the vac line into the air distributor plenum.

[EJP914]

Thanks for the replies. In response…

Cold start valve unplugged. Will route gas line around it and see what happens.

MPS will hold vacuum for over 30 minutes or longer. Do you guys think I will get results by adjusting and adjusting screws in back or bite the bullet and get a new rebuilt one?
They are pricey.

Car does start and run but very rough. Can I assume CHT is ok?

Car was in shop for 4 months and they could not fix it. Brought the car home. Very first thing was oil and filter change. I use 20/50 oil. Oil drained out like water with heavy gas smell. Will have to do it again soon.

Replies are appreciated. Thx

Ejp914

[emerygt350]

I would never assume the cht is good. It has a very strong affect on the richness. If that is reading high resistance your ECU will flood the cylinders no problem. Check the resistance on that thing. If it is high, that could be it. You have the mps vacuum line hooked up to the plenum? What kind of vacuum is your engine pulling at idle? Plug your mighty vac into the line that normally goes to the decel valve and find out.