88 no start problem -- looking for the easy way out

[tubwreck]

Stock '88. About one in 20-30 times trying to start it, this is what happens:

- Key on (oil light on, alt light NOT on)
- Key to 'start' and you get...
whirring fuel pump
big click/clunk from under the back seat

Sometimes, if you try 15 or 20 times, it starts. Sometimes if you are lucky, put it in 3rd gear with the clutch up and nudge it while holding the key in 'start'.

Should I just bite the bullet and by a digital VOM and run the full diagnostic procedure, or is there a 99% chance that it is the starter motor?

Any suggestions appreciated!

[Wil Ferch]

You are *not* getting "whirring " of a fuel pump.... it's something else.

Unlike ( maybe) CIS cars...DME cars have a "start permissive" in the circuitry that won't allow the fuel pump to run unless it is "sensed" that the motor is actually spinning...

A safety feature for when the car ends up on its head and you don't "feed a fire".....

- Wil

[tubwreck]

I'm pretty sure that the fuel pump runs when the *starter* circuit is engaged -- otherwise there would be no fuel provided to the engine during cranking.

The other borderline odd thing is the Alternator light. Sometimes on, sometimes off.

[ruf-porsche]

Is the engine turning over when you try to start it or just a whirling sound. Could be a bad solenoid on the starter.

[DW SD]

The fuel pump doesn't run unless it sees that the crank is turning via the crank position sensor. The computer actually gives the pump power via DME relay stage II.

When you say it starts, does it run or is it merely cranking?

I would guess the clunk from under the seat is the starter relay. Are you sure the battery is charged? What happens to the voltage at the battery when you turn the key to crank (does it drop WAY down?)

Another test would be to check voltage at the starter when you turn the key to start.

I'd check to make sure you have a good chassis ground. That could effect the alternator light (if I remember the alternator idiot circuit properly).

Doug

[Wil Ferch]

quote..." I'm pretty sure that the fuel pump runs when the *starter* circuit is engaged -- otherwise there would be no fuel provided to the engine during cranking. ..."

Why do people ask questions and then argue against the facts ....??

yeah...maybe when the "starter" circuit is engaged AND it is sensed that there are actually RPM's during the start attempt !!! ......

no rpm's...no fuel pump running !!!

- Wil

[ruf-porsche]

Originally posted by Wil Ferch
quote Why do people ask questions and then argue against the facts ....??

yeah...maybe when the "starter" circuit is engaged AND it is sensed that there are actually RPM's during the start attempt !!! ......

no rpm's...no fuel pump running !!!

- Wil

Because they like to argue?

[ischmitz]

A voltmeter would certainly help here Check the battery voltage, check if the alternator is charging, check if there is a voltage drop somewhere (ground strap, battery connectors, connectors at the starter, etc)
Without that it's just wild guessing.....

[rick-l]

Originally posted by ruf-porsche
Because they like to argue?

If you look at FR Wilks schematics Pin 4, which comes from the starter solenoid, is ORed with the DME command that drives the DME relay pin 20.

That might be the fuel pump

[2.7RACER]

Ed,
You can buy a decent meter today for less than $20. Harbor Freight for less than $5.
Unless you are clairvoyant, you'll need the meter.

[rick-l]

Originally posted by 2.7RACER
Unless you are clairvoyant, you'll need the meter.

Not necessarily, although nice to have (but know how to use it also).

You know the ignition switch works, the Fuel Pump Runs.
That big clunk is the solenoid trying to pull in.

This does not sound electrical in nature to me. Time to get dirty and look at the starter/solenoid .

[ruf-porsche]

Originally posted by rick-l
Not necessarily, although nice to have (but know how to use it also).

You know the ignition switch works, the Fuel Pump Runs.
That big clunk is the solenoid trying to pull in.

This does not sound electrical in nature to me. Time to get dirty and look at the starter/solenoid .

Originally posted by ruf-porsche
Is the engine turning over when you try to start it or just a whirling sound. Could be a bad solenoid on the starter.

I guess you miss my previous response.

[rick-l]

Originally posted by ruf-porsche
I guess you miss my previous response.

I understood the symptoms to be a loud clunk and the engine not turning over. (0 RPM)

To me this would mean the contact in the solenoid that energizes the starter winding is not being made either because the contact is bad or the contact is not closing due to the gear hung up and not engaging the ring gear allowing the contacts to close.

Either way starter removal / exam is required unless you just want to shotgun the whole assembly, which may not work either.

[DonMo]

A volt meter and the diagnostic page out of the Bentlleys for the Motronic should help you. You disconnect the connector to the ECU and check pins and find out a bunch of useful info. Meter on VAC and engage starter will tell you if you are getting reference and speed sensor readings. You can check grounds, you can pin out the connector and hear your fuel injectors engage, you can pin out connectors and make the fuel pump run. Here is the pin layout, let me know if you need the diagnostic pages.

[Lorenfb]

"yeah...maybe when the "starter" circuit is engaged AND it is sensed that there are actually RPM's during the start attempt !!! ......"

No, only needs to "see" the #50, i.e. the starter signal @ pin 4.

[rick-l]

Back to the original topic

Ed

Any luck with your starter? No loose cables (the big one)? Does moving the car in gear allow it to function? Can you jack it up and beat on it when it doesn't work?