85.5 944 starting problem

[domlato]

I need some suggestions to solve starting problem. I have replaced in this order 2 crank switches, dme, fuel pump, coil. would not start. When cranking starter fuel pump was working but coil was getting power to the coil but not sending power to distributer,
While cranking using a probe connected to battery and touching the negative post of coil the engine started. Thought might be a problem with computer sent the computer to
AES MODULES to have checked. After checking it was determined that computer was bad but could not be fixed so replaced with factory rebuilt computer. Now the problem is switched from getting signal to coil to fuel pump not working. but using starting fluid while cranking engine starts.
Any suggestions???

[Jfrahm]

See if it runs with a DME relay jumper.
Consider alarm wiring? Or an issue with the DME relay socket in the fuse box.
Could also be the injector harness or 14 pin connector
https://rennlist.com/forums/924-931-944-951-968-forum/1176292-14-pin-connector.html

[domlato]

Thanks, I will relay info to mechanic

[Ontarioporsche]

Keep us updated if you get it figured out! I have a 1985.5 I’m trying to figure out a non start/no spark issue!

[walfreyydo]

I would refer to this page:
https://www.clarks-garage.com/shop-manual/ts-01.htm

[domlato]

Thanks to all that offered suggestions. Problem now worse nothing working now. Guess we start from scratch and have computer checked unless there is a way to check the computer without removing and sending to have it checked.

[Monkey Wrench]

if you went ot a mechanic that specialized in 944's he may have a ECU ( or in porsche lingo a DME) that he could use as a test. otherwise if it is not the computer you just wasted money.

"shotgun troubleshooting " is a technique often used by those who are less familiar and they may save by buying more parts than needed but save by not paying shop mechanic rates.

If you have a "proper mechanic" doing that, and charging a hefty hourly rate, then it may be a questionable method of troubleshooting.
Perhhaps he finds the problem faster? Perhaps you just end up buying a lot of parts your car does not benefit from? You get to be the judge of that

a process of ellimination is a different technique, in that case the mechanic is replacing perts or doing tests in some orderly fashiopn with the point being to narrow down and isolate the problem.

If you spend time and follow the suggestions on Clarks garage this is probably a great process.

If you like the mechanic and feel he still needs a little "help" you could print some of it out for him to follow. Every great mechanic may not be fully familiar with the 944.

id ask this,,
"if you want ot order a new computer to test if the computer is the issue, and it turns out thi is NOT the problem, who pays for it? how much is it? "

- at least you have an answer instead of an expensive suprise .

a more savvy owner may ask the mechanic " have you verified if the DME has power and ground during cranking? " what evidence do we have that the DME is or may be the issue?

if the mechainc isnt; even sure the DME has power and ground yet he is ready to spend YOUR MONEY that may be a sign you are at the wrong shop?

some parts like sensors may be replaced because they are old and wires may be hardened etc, doing so may increase reliability.

an example the car is 35 years old and so is it's fuel pump, well you may choose to not wait for the point of failure. it certainly wont happen at your convenience.

in this case lets say it is pumping lots of fuel it has fuel pressure,

by replacing the pump at this point , you are likely not any closer to the reason for your no start issue.

the mechainc will hook up a fuel pressure guage and or or check the fuel flow, if no problems are found the pump is pumping he can move forward to other items in a logical sequence of troubleshooting. he knows this is not the cause ( possibly intermittent, rare but possible)

the DME relay latches turning on the fuel pump and as well the DME, Just because it is pumping may not rule out the DME relay. it has two functions.

You can buy a solid state DME relay with some indicator lights to help troubleshoot the mechanic also may check the DME to see if it gets full power when the relay latches during starting.

another mistake or (trap) we can fallinto here is by using shotgun troubleshooting and failing to remove the part he puts in after seeing no difference.

what can happen is the part is bad And it was also not the real issue, next you have a car with TWO reasons why it won't start.

this is where you start to see clumps of hair accumulating

when you have not found the problem but you see conditions changing in your troubleshooting watch out! go back undo the things that you ddi that made no difference or changed things

See if you made a mistake Perhaps it is a bad part, maybe you accidentally
unplugged a wire? Find the reason for that change before going ahread to other items. if you do not, this is whats known as ..

" digging a hole for yourself"

could it happen that the mechanic is thinking, gee im sick of trying to find this issue, but I cant; say to my customer look Im completely lost and I cant; find the issue, that could ruin his reputation.. and then he things ok,, "well sir" I think we should replace the DME board"

lets assume for a minute, he knows it is a DME is thousand beans, he'll mark it up to $1500, As a result of saying that, he will either make a little profit or chase you down the road, He is tired of chasing the probem, feels a bit lost, He's at the point of the realization that this job isn't looking very profitable

this could be his way out or a way ot make more profit, Yes I could be completely off base on this, You get to decide ;-)