84 Carrera - no start

NoLift911 · 03-11-2021, 01:44 PM

So have been away from the forum for a loooong time...car has been sitting for 6 months. It cranks fine, but no start, checked fuel pump fuse, cleaned terminals getting continuity. Still no start. Changed out DME with another spare I had, still no start.

With ignition on should I hear anything fuel pump buzz etc? Anyway with the ignition on there is no power at the fuel pump fuse block - should there be? I think I read only power at the fuel pump during cranking or running...so also no power at the fuel pump with ignition on. Put 12 volts to pump and it spins so pump is good.

So - after 25 years of ownership, car has not ever not started and that was the extent of what I needed to do and it always seemed to work. So not sure what else to test next...I guess my second DME could be bad?? Odds of that are....high.

Don't want to replace parts for no reason, was running fine when I parked it in the garage so nothing else changed.

I definitely did not smell fuel when cranking - and I think I always smell fuel.

What else to check - ?

Jeff

proporsche · proporsche's Garage

there is no fuse for the fuel pump.Do you have any alarm or kill switch on your 911..you will not hear the pump with the key on.
let us know then we go further

Ivan

Driven97 · 05:42 PM

I have $1 on crank and/or reference sensor. I had mine flake out in the middle of day 2 of a two day autocross. With much fiddling, and probably a lot of luck, I got it to fire once. Drove 230 miles home without shutting the car off.

Closest I've ever been to the car stranding me.

Driven97 · 03-11-2021, 05:04 PM

If you search someone posted the procedure to check the sensors with a voltmeter.

proporsche · proporsche's Garage

mysocal911 · 03-11-2021, 08:03 PM

Read here; 911 3.2 No-Start Troubleshooting

NoLift911 · 03-12-2021, 05:59 AM

Thanks will start to troubleshoot - somebody mentioned there is no fuse for the fuel pump, that is incorrect, just want to document for others. This is an 84 Carrera.

gomezoneill · gomezoneill's Garage

Quote:

Originally Posted by driven97

i have $1 on crank and/or reference sensor. I had mine flake out in the middle of day 2 of a two day autocross. With much fiddling, and probably a lot of luck, i got it to fire once. Drove 230 miles home without shutting the car off.

Closest i've ever been to the car stranding me.

this

NoLift911 · 03-12-2021, 07:16 AM

So with the reference/crank sensor does this impede gas flow? I can't smell any guess when cranking, hence why I went down the fuel trail first....

Driven97 · 03-12-2021, 07:29 AM

If there's no signal from one of the sensors (I forget which one) it doesn't trigger the pump.

76FJ55 · 03-12-2021, 07:30 AM

the crank and ref sensors tell the computer that the engine is turning, and in kind the computer turns on the fuel pump through the DME relay. you will not get fuel without good crank and ref sensor. have you checked spark? you will also loose spark if the crank and or ref sensor fails.

wjdunham · wjdunham's Garage

Quote:

Originally Posted by 76FJ55

the crank and ref sensors tell the computer that the engine is turning, and in kind the computer turns on the fuel pump through the DME relay. you will not get fuel without good crank and ref sensor. have you checked spark? you will also loose spark if the crank and or ref sensor fails.

Not quite - the reference sensor is only used after you release the ingnition key from the start position. In the start position, the start signal overrides the reference sensor and turns the fuel pump on. Disconnect the starter wire and you should hear the fuel pump running in the start position.

Bill

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by proporsche

there is no fuse for the fuel pump. Do you have any alarm or kill switch on your 911..you will not hear the pump with the key on.
let us know then we go further

Ivan

Ivan,

Check the wiring diagram/s for Carrera 3.2 and you will find the FUEL PUMP FUSE @ #16 (this is the 16th fuse from the front to rear of the fuse panel).

Tony

proporsche · proporsche's Garage

Tony....my bad what was i thinking ;-))))))yes it is ..no 6 from the windshield;-)
Must have late at night when i wrote it;-)

Fuse it is but not fuel pump relay....

Ivan

proporsche · proporsche's Garage

Quote:

Originally Posted by NoLift911

Thanks will start to troubleshoot - somebody mentioned there is no fuse for the fuel pump, that is incorrect, just want to document for others. This is an 84 Carrera.

That idiot was me ..who said it ..of course there is a fuse, check the one number 6 direction from the windshield..sorry must have been early morning when i wrote this crap;-)

Ivan

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by proporsche

Tony....my bad what was i thinking ;-))))))yes it is ..no 6 from the windshield;-)
Must have late at night when i wrote it;-)

Fuse it is but not fuel pump relay....

Ivan

Ivan,

It takes courage and discipline to admit your mistake. I committed a lot of mistakes too. But there are some people who would not admit or acknowledge their mistake specially in an open forum because of vanity. I have high regards for you.

Tony

gomezoneill · gomezoneill's Garage

Quote:

Originally Posted by proporsche

That idiot was me ..who said it ..of course there is a fuse, check the one number 6 direction from the windshield..sorry must have been early morning when i wrote this crap;-)

Ivan

You think you know more than you do and post way to much.

proporsche · proporsche's Garage

gome... have to admit, i do not quite understand what exactly is on your mind;-)

If i post too much.. sorry if that bothers you;-)....nothing else to do if you are waiting for parts for engine rebuilds;-)

Ivan
what i know is more or less from working on 911`s for 39 years......

proporsche · proporsche's Garage

Quote:

Originally Posted by boyt911sc

Ivan,

It takes courage and discipline to admit your mistake. I committed a lot of mistakes too. But there are some people who would not admit or acknowledge their mistake specially in an open forum because of vanity. I have high regards for you.

Tony

Tony, i blame covid...plus i`m on the vagon for 4 month plus waiting for parts for rebuilding 3 engines gives me too much time to do nothing;-)so 3a.m. is my normal time to go night night and brain is not working strait.....

Ivan

gomezoneill · gomezoneill's Garage

Quote:

Originally Posted by proporsche

gome... have to admit, i do not quite understand what exactly is on your mind;-)

If i post too much.. sorry if that bothers you;-)....nothing else to do if you are waiting for parts for engine rebuilds;-)

Ivan
what i know is more or less from working on 911`s for 39 years......

I respect you but I was factory trained in Nayac NY in the early 70's. You just seem to jump to diagnoses sometimes too soon no disrespect intended. It does not bother me at all just a observation.