Odd start '88 Carrera: is this a fuel pump problem?

[Bob Prosser]

Hey Guys. Help me with a sanity check on my 3.2 Carrera weekly driver.



In the fastidiously-maintained 170K miles since new, it's been bulletproof, and always starts on the first tap of the key.

However, twice in this last year (last time a week ago), it wouldn't start like that -- it would crank and crank and crank, but not catch. Not even a sputter. We're talking 5 or 6 attempts of cranking for approx 5 seconds each time. Then, after a few minutes of wondering what's up, on the next tap of the key, it starts instantly. And it runs great after that. Weird!

Only clue I can give you is it's been after sitting for a few days. No smell of fuel. No fuel pump buzz. Ground straps seem clean and tight. The battery seems strong enough to crank the engine over plenty fast.

I suspect the original fuel pump needs changing? It's not growling or making any noise.

Or another fuel pressure-related issue -- but what? I replaced the fuel lines to the fuel rails a few years ago.

Thanks for any and all input!

[jlex]

Try replacing the DME relay under the seat. My old Volvo behaved the same way when its relay was going bad. Sometimes you'd crank a lot w/ no go, then sometimes it'd start right up. Cheap enough to change out; you should have a spare for your 3.2 in the glove box anyway. Try the relay first & let us know...
regards,
jlex.

[Bob Prosser]

Not a bad idea, and easy enough to do. Thanks.

FYI, I replaced the relay a few years ago as a preventative maintenance measure, and yes, I do keep a spare in the car.

Any other ideas anyone?

[jlex]

Go thru this diagnosis when it's acting up (previously posted by Ingo):

You need to do a systematic diagnosis rather than throwing parts at it - the standard answer of "change the DME relay" or "replace the sensors" doesn't make any sense without proper investigation. Most of that can be done easily without any special tools. A 3.2 DME is not very complicated. Here is a quick list of checks:

- check if you have power to the DME with the ignition to ON (ICV vibrates with the key to ON) if not it could be the DME relay or factory alarm if present

- verify that your fuel pump comes on during cranking (test light on the correct fuse), if not it could be a bad pump, fuse, or DME relay

- check if you have spark (old plug connected to one spark plug wire while an assistant cranks the engine), if not it could be a bad DME, or one of the sensors, check the sensor resistance to be close to 1000 Ohm.

- check whether you get fuel injector signals (LED test light while an assitant cranks). If not same as above.


If you get one but not the other it is either something downstream (coil, rotor, cap) or the DME but NOT the sensors

Finally, for more advanced checks you need a fuel pressure gauge, an oscilloscope. The engine should start even with cylinder head temp sensor being bad, O2 sensor being bad, AFM being bad but run badly. My guess from experience is that if you have fuel but no spark you either have a bad coil or a bad DME. Hope that helps,

Ingo

[Bob Prosser]

Thanks Ingo. Your recommendations are for a more consistent and repeatable problem. As you see in my original post, the problem is rare, and when it does happen, the car starts within minutes -- as though nothing ever happened.

But if this problem gets worse, then your input will be very helpful indeed.

In the meantime, I am going to swap-out the DME relay for a new one (the one in there is 5+ years old). I also just learned that it incorporates the fuel pump switching as well -- more indication that this is the right item.

Best to all.

[jlex]

BTW: that is one beautiful car. Finish looks flawless. Enjoy!

regards,

jlex.

[Bob Prosser]

Yup, thanks ... I've had others, but this one has always been my old-school favorite. I've owned it so long, I can't get rid of it now.