Ricardo Vega II

Hey guys, I'm a new member here on Rennlist and been a 3 month old owner of a 1987 Porsche 928 S4, that hasn't given me any problems at all and everything worked on fine on till today. I tried to start it and nothing! Has a half tank of fuel, pump has power to it. It pumps gas to engine block since I loosened coupler at T section when I crank it. The spark plugs have spark, took one off on each side of engine and tested them and had spark to them that grounded to anything metalic in engine bay.
Having gone thru the basics what else can I possibly check before having to haul car to a mechanic? Can it be possible that timing belt jumped or skipped? I have the service record here that it was done about 30,000 miles ago. The car has 85,000 on it.
I've never had this car before so I can't even begin to tinker on it like most of you guys can. Could a diagnostic tool be of any help? Or is it something that a Porsche mechanic can only know what might be an issue with? Thanks!

Ricardo
1987 Porsche 928 S4

mickster

Okay you have fuel and spark-are the injectors opening?

Any dash lights-anything at all?

I hope there is an El Paso member here. Most are on the other side of the state...

James Bailey

You need to crank it over several times then pull a spark plug to see if it is wet with fuel....you may have a bad injection relay , injection brain etc.so check for fuel on the plug. You can pull one of the plastic air intake ducts and look at the timing belt through the vent hole if some one else cranks the engine you can see the belt moving..If it has jumped time you are not going to cause any more damage by cranking it but the belt timing is probably fine.

mickster

That was what I wanted to write but couldn't articulate. The people on this board are awesome!

James Bailey

Thanks I have had a lot of practice

mickster

Oh I know!

SeanR

Go to Autozone/Napa and get a fuel injector noid light. Then you can pull off the connector to one of your injectors, plug this in and see if you have an injector pulse. Tell us what you find and we can go from there.

Ricardo Vega II

Michael and James, I totally appreciate your help! My rookie butt is a new 928 owner and realizing now that this car is pretty complicated! Either way I have been totally floored on what technical marvel this car is! Amazing and wowed almost everytime I take apart something, such as the fuse panel, that there is a fuse tester in it. Like seriously?
As far as what you guys asked I didn't even bother on checking but now know.
@ Michael, nothing turns on while turning over engine on panel.
@ James, ill have to check plug in the next day or two when I go back to my girlfriends house and check what you said. I did have my dad, who helped me out, look into the holes where the timing belt is at and check it as I turned it over and said the belt rotated inside them.
Like I've said, excuse my ignorance but this is my first time owning this machine but to put it simple terms, this issue can be coming from it not allowing even the injectors not opening and allowing fuel into cylinder? Even though there is fuel pressure in the rails there is an electronic signal that won't allow into the cylinder?
I did google a few times my issue and also found a few people saying that one can pin point issue by swapping out relay between horn and injectors and check if that is the case. Is that right? Relay 30 for 87? Thanks!
Ricardo

mickster

Follow what Sean said; relays may be your saving grace here but if it's the LH computer, then it's a different game you'll be playing.

WallyP

One check that has not yet been mentioned: Lift the hood. Turn the ignition switch on (don't spin the starter). Listen carefully - do you hear clicking from the injectors?

If so, the LH (injection) ECU (Engine Control Unit or computer) has failed - not too rare on these cars.

If no clicking, time to move on to other checks. To quote a very smart man, "Relay, relay, relay!" There are some relays that must operate correctly, or the engine will not run.

Fuel pump relay is the most common failure - if you can hear the fuel pump buzz or whine while the starter is operating (kneel by the rear bumper), the fuel pump relay is OK, and that means that the ignition relay is probably OK as well.

Get a mechanic's stethoscope (cheap at Harbor Freight, not bad at most auto parts stores) or three feet of plastic or rubber tubing, 3/8" or bigger. Stick the tube in your best ear, and put the other end on one of the injectors. Have someone spin the engine - you should hear regular clicking. If not, swap the injection relay (XXV - use a flashlight to read the Roman numerals, and make sure that you understand which relay is which) with the horn relay (XII). Try to hear the injector again.

Let us know what you find. Be verbose, be precise.

rbrtmchl

If the problem turns out to be a relay, the 928 Specialists site has a very useful fuse and relay chart for each model year 928. Here is the link. Click on the + next to '928 Fuse/Relay Charts' and find your model year. Print out these charts for future reference.

https://www.928gt.com/default5.htm

Kiln_Red

I agree with Sean and Wally. I'd rule out the LH (injection brain) first. And if you are sure that you have fuel delivery and spark, this virtually narrows it down to injector pulse or valve timing for possible issues as you said this car has been recently reliable. Follow Wally's suggestion of listening for the injectors to click with the key on. If you're unsure, go get a NOID light down at the parts store as Sean suggested.

outbackgeorgia

My 87S4 had the LH computer fail at about the same mileage, but symptoms were different.
You may have a crank position sensor connector failure as I did. The connector plastic housing just crumbles. Your Tach needle should be moving ( bouncing) as you crank if the sensor is good. If no tach movement, dead sensor input, probably the connector.
Dave

rgs944

Where is the location of the CPS connector?

Kiln_Red

Normally, this would be a good suggestion. In this case, though, the OP has indicated that spark is present, so the CPS is sending its signal.