Firstly, thanks in advance for any help here. I've read several threads here on my problem, but need a little more assist.

87' 924s, 18k miles (likely 118k) - Won't start - Been sitting for several years (in an actual barn

Symptoms:
1. Fuel pump will not run when key is turned on (replaced pump, didn't fix the issue)
2. No Spark
3. Injectors don't smell like they're actuating (no fuel smell at the exhaust)
4. No tach bounce
5. Turns over fast, (new battery)

Steps already performed:
1. Replaced the fuel pump, no change
2. Replaced the fuel pump relay, no change
3. Made the relay bypass pigtail from clarks-garage
a. Fuel pump runs now, but no spark, no fuel out the exhaust, or tach bounce

It appears the previous owner might have been troubleshooting the same thing when it was parked. There are two sensor plugs on top aft of the motor that have been disassembled (pic attached). I would reassemble (or fabricate a new plug), but I don't know which wire goes where and the wiring diagram I've found doesn't show the connectors. Also, I don't know which plug goes on top or bottom to match them up. I suspect from reading other posts, that I need to get these two sensors corrected before doing any other troubleshooting.

Thanks in advance!
Jeff

 

Take a look at the speed and reference sensors, or wiring - thats what those plugs appear to be in your photos. You might need to buy new ones as they are very sensitive to electrical interference (note the grounding insulation on the wiring). These sensors are critical because they tell the DME where the engine is in its timing cycle.
http://www.clarks-garage.com/shop-manual/ign-02.htm

Without a running signal from these sensors, the DME wont activate the injectors or send secondary voltage to the ignition coil. See "engine cranking/running signals" section
https://www.clarks-garage.com/shop-manual/fuel-16.htm

This might also help you:
https://rennlist.com/forums/924-931-...epair-kit.html

 

Walfreyydo,

Thanks much for the quick info! I found those wiring diagrams, but they appear to be for 78 (I need them for 87). I'm thinking that a lot would be different after 9 years.
As soon as I can figure out which wire / plug is which I'll follow those t-shooting steps. I'm stuck until I get those two plugs wiring figured out and reassembled.

Cheers,
Jeff

 

I updated my comment above after doing a bit more research. As you mentioned the wiring diagrams werent clear. You may want to look at an early 944 diagram but I am not sure if they are similar.

I found something on page 80 of this (83-87 944)but its showing the speed/reference as having only two wires which doesnt seem right (both yellow and black wires).
http://p914-6info.net/944_Manuals/Vol4-electrical.pdf

Also page 28 here (88 and up 944) - Looks like the third wire (brown?) is a ground whereas the other two feed into the DME.
http://p914-6info.net/944_Manuals/Vol5-electrical.pdf

Either way it might be better just to purchase new sensors which should come with the needed plug. Remember to gap them properly.
https://944online.com/aftermarket-reference-sensor.html

 

Those reference sensor connectors are molded with the wires inside and not intended to be serviceable, they should both be replaced along with about 4,000 dollars of other parts before expecting to be driving this one. Is it too late to put it back in the barn?

 

Walfreyydo,

Thank you!!! Just ordered two replacement sensors and will report back after I install them. The Second diagram looks like it. Odd that Porsche reversed the wire colors on those two sensors for the harness into the DME.. (Not the strangest thing I've ever seen on a schematic though.. ha ha).

Cheers,
Jeff

 

Ouch! Maybe warranted... but still... ouch. (I mean no disrespect... Gage has given me great advice on more than one occasion! )

The following is thrown around a lot in this forum. It's been thrown at me. It can get a little annoying... but it absolutely, positively doesn't mean it isn't worth doing...

Have you gone through the troubleshooting at Clark's Garage? Start with getting the fuel pump working.

HUGE EDIT... Just saw you got the fuel pump working after jumping per Clark's. Completely disregard what I wrote above. I'll try to find some other way to be helpful!

 

That's my bad on the sarcasm. It wasn't intended to sting but rather to balance the naive optimism common to folks new to this car and process and say (albeit with failed sarcastic humor) there is more than likely a long road to resurrecting a 35 year old sports car.

 

Gage, I was just going to ignore your out of place comment. Since you posted yet again something that has zero positive impact on the issue at hand... I'll say; If being snide and sarcastic while providing ZERO assistance makes you feel better about yourself, you have issues. This is just a car. Nothing more, nothing less. Just a car. I appreciate the wealth of information on Clarks-Garage and this forum. No doubt it's saved me quite a bit of time in my troubleshooting already. You have no idea who I am, and I really don't care. I will say spending a few hours tinkering on this car is one of the simplest things I've done in a very long time. I engineer "things", software, hardware and firmware (software design, network design, electronics and microcontroller design and programming). If you took a moment to read my first post, and really absorb the content. You might have gotten an idea your snide comments are very much out of place. They provide no benefit other than trying to make yourself feel superior. Feel free to post something constructive on the issue. Otherwise, please just go away.

I look forward to engaging others here in a constructive manner, and very much appreciate the information Walfreyydo so helpfully dolled out.

Cheers,
Jeff

 

Did replacing the speed/reference sensors yield any fruit? Guess they are probably still in the mail.

Let us know when you get a chance to replace.

 

Walfreyydo,

Yep still waiting on shipping. I'll post once I get them replaced. Thanks again for your help! It's much appreciated.

Cheers,
Jeff

 

I think you will find that an overwhelming majority of folks in here are helpful, and friendly. There is a wealth of 944 knowledge here, collectively.

 

You should also consider pumping the old gas out of the tank but until you get the new sensors in not much else you can do. If you happen to hook the sensors back wards it will not hurt anything but you will get no start, (others does that sound right?) also those injectors are going to be gummed up. Go out and start shooting PB Blaster on the sensors NOW so it can start sinking in, those sensors can be really hard to remove.

 

It looks like the new sensors will be here Tuesday.

DHS928, I've already drained the tank and ran about a gallon of fresh gas through the fuel system, up to the mainfold. Great idea on proactively PB soaking the existing sensors. I was hoping to evaluate the injectors once I got the DME going, but since I have a few days. I might go ahead and pull the injectors and soak them as well.

Thanks everyone!
Cheers,
Jeff

 

I'd also purchase new leads that go from the sensors to the DME. 944online.com sells a handy kit for this. The signal generated by those sensors is extremely weak, so the connections and wirings needs to be in top condition for reliable operation. Regarding other stuff you should expect to do to the car...it will be a lot, unless you don't mind it breaking down all the time. I have an '87 924S that had been sitting for a long time. I spent probably 20k on it and dug like 7 or 8 mud dauber nests out of it before hitting the streets with it. But it's been 100% reliable in the two years I've been driving it as my primary mode of transportation.