New to me 87 930 No Start Issue

SG930 · 11-08-2023, 08:03 AM

I have been driving my new to me 87 GP White 930 for a month. Since it's new to me I want to get a ground zero for maintenance so I added some techron to the gas tank and went driving. Had a cold start time of 4 to 5 seconds so I thought I would add the techron since I have no idea on the gas age/condition.

Cold start issues continued as I went through the tank of gas (premium 91) and then another. Warm starts were faster 1 to 2 seconds of cranking.

I read a lot of the forums and did research some great posts here so I decided to go the cold start trouble shooting route. Replaced fuel filter since again, no history. No change in start up. Took off the AAR to check and it tested out fine. No change in start up (hard start, 4 to 5 seconds). Cranking became slow so I replaced the red top optima battery. It was estimated at 15 years old and did not test well. New battery is awesome with great cranking power. I did adjust idle speed to 900 after warm. It was at approximately 700.

Convinced my wife to go for a long Sunday drive. It's colder this time of year in WI so we have the wineries all to our selves apparently. After first stop, about 45 minutes, the car cranked for a long time and finally caught. Like 10 to 15 seconds. I didn't like cranking that long but we were 75 miles from home. It eventually started and idled perfect at 900 RPM. We then worked our way home and stopped for some dinner. One hour later, same thing. She agreed no more stops on the way home.

The car died pulling into my driveway after an hour of driving home that night. Pooping the clutch would not work either while rolling. Pretty lucky though. Car cranks well but no fire. Pushed it to the garage and waited until the next morning and same thing. This is now a no start trouble shooting journey.

I opened up the frunk to see that I luckily own a car that has the 2 individual mini spade fuse modification for the fuel pumps and the head light relay modifications ( Thanks ShadeTree930!). Opened the engine bay and driver side (left) relay/CDi compartment. Found a pig tail off the yellow boost relay loose (See Photos).

I cleaned up the relay prongs and will get the CDI sound along with fuel pumps running with key turned turned on as long as the pig tail is grounded. Ungrounded and no fuel pumps or CDI sound. It may have come loose and that is why the car died? Doesn't seem like a good connection to be loosely grounded in the fold of the light gauge metal. Red wire looks a little "cooked" as well through the rubber grommet.

I get a good soosh(?) sound when manually moving the metering plate down too. I do have a temporary horrible sounding dash noise that's not the door being open noise while in the on position. Ignition? Car cranks well just no start. Speed relay?

I'll guess I research spark next. I'm not a good electrical sleuth and this is not the car to throw the parts cannon at. I do have the CDI noise (doesn't it mean it's good), fuel pumps are working (therefore fuses and relays too) and the WUR inlet is clean. Any input on the pigtail relay would be helpful and appreciated. I eventually want to get to control, cold and warm CIS pressures (gauges coming soon). I did have very loose intake nuts and one missing. Thought that would effect the hard cold start but did not. Need to smoke test.

Car is definitely modified with a BL adjustable WUR, rebuilt fuel head, Fabspeed intercooler, K27 turbo, headers BnB exhaust. There's an aftermarket rev limiter(?) before the CDI box too. Engine top was rebuilt by Mirage approximately 5K miles ago. Currently at 79K miles. Car runs awesome when it runs.

Sorry for the long explanation/story, typos, brevity, etc. Just seems like there is so much to check especially going from a cold start problem to a no start problem.

I catch on quickly after a long time.

Mustangkev · 11-08-2023, 01:13 PM

I believe the relay pig tail should be attached to the nut just behind the relay.
I thought the relay with the pig tail was only for the ‘86. The relay for the 87-89 doesn’t have the pig tail and is part number 911.615.118.01

slyguy · 11-08-2023, 05:19 PM

At the very least you must verify fuel and spark otherwise you're chasing everyone else's experience with a no start. CDI sound doesn't guarantee spark, fuel pumps simply making noise does not guarantee fuel, etc. overboost switch fail can prevent start. 14 pin connector can be misbehaving.
Heres an older yellow relay thread

https://rennlist.com/forums/911-turbo-930-forum/315180-what-s-so-special-about-the-magic-yellow-relay.html

SG930 · 11-09-2023, 05:02 AM

Thank you. I should have my CIS gauge here this weekend to check no start pressures. Car won't run. I will do a quick flow check too and test the CDI box and ignition coil ( need to research safe ways for CDI and coil). I learned the pigtail connected keeps the fuels pumps on with ignition on. The pigtail disconnected keeps the fuel pumps off with the key in the on position until the air meter plate is moved, then they kick in. Either way should not have made the car die. I still get this terrible sounding noise (alarm?) in the dash. Also, looks like someone had bee in the ignition wires too based on electrical tape. I'll focus on spark and fuel first.

Thank you.

slyguy · 11-09-2023, 09:53 AM

Induction timing light on coil wire will tell you if you're getting any action out of the coil into the cap. I pull plugs to see if they're wet, if they are of unknown age replace them.

SG930 · 11-10-2023, 04:59 AM

Another follow up: Per kellcats521 and 911SauCy, I checked the resistance between pins 7 and 31D and the CDI connector for resistance and got 600 ohms. Then I switched to VAC while cranking and got varying low voltage. I used a power probe like device. Also got 12v at pin 15 and checked ground at 31/1.

Next I removed the tach connection at the tach, removed wheel and upper plastic to get out) and tried started after reconnecting CDI. No start with or with out tach connected. Not sure if I mentioned that I had a jumping tach before I switched in a new battery. By this diagnosis, it would lead me to believe the CDI box is dead.

This is an expensive fix. Any recommendations on brand, vendor for replacement?

Thank you.

908/930 · 908/930's Garage

So you determined you have no spark? Prior to removing too many things my tack tends to bounce up at times, has done it for 15 years. The ignition coils are known to fail also there is a small green wire from the distributer that triggers the CDI that is also a weak point.

If it is the CDI they can be rebuilt.

SG930 · 11-10-2023, 12:19 PM

Green wire looks good and tested good by resistance from pins 7 and 31D. I need to get power to my timing light and put that on the coil wire tonight as suggested. May pull off the ignition coil too since the Fabspeed intercooler is easy to pull off.

SG930 · 11-14-2023, 04:44 PM

Good news. Car runs now. Bad coil and bad CDI box. Starts fast and idle great. Needs pig tail on yellow relay connected to start. Bad news is no Tach and the boost gauge is pegged out. The only thing I can think of is that's is modded with a rpm switch, at least for the tach. The new box and coil are from Parts Klassic.. See picture of Rpm device.

slow&rusty · 11-15-2023, 03:27 AM

Congrats!

Where did you source your new CDI box?

SG930 · 11-15-2023, 05:05 AM

The box and coil are from ************. I have only had the car a month but I never experienced starting with the key and no throttle like it will now. Boost gauge is all good now. I was too much in a hurry and forgot to hard connect the intercooler. Still no tach gauge. Original tach with a very tight connection. Tough to get out too.
The white cable of the "RPM box" (?) ties in to the black/purple of the CDI wiring. There is also a black ground and the a red that ties into an existing red/white on the right side of the engine and then a grey wire. The grey and red go to a solenoid switch attached to the WUR that then goes to the cut off valve.

SG930 · 11-15-2023, 05:12 AM

Sorry about that. Kind of new to this forum stuff. I guess this is the trouble of modified cars. Not sure what will happen if a disconnect that box and reconnect wires. The grey wire appears to be the only new one. No guarantee the Tach will work after disconnecting. My tach did bounce once when I got the car a month ago just before a replaced the battery, otherwise it worked.

908/930 · 908/930's Garage

good to hear your car is running again, quick start up is what it should do pretty much as soon as you turn the key. Check where you ordered the CDI about the tach not working, take a look at the install again, I remember some problems with tack problems with some MSD boxes and can't remember if the trigger signal was switched + for -.

gorskined · 11-16-2023, 10:29 AM

Quote:

Originally Posted by SG930

The box and coil are from ************. I have only had the car a month but I never experienced starting with the key and no throttle like it will now. Boost gauge is all good now. I was too much in a hurry and forgot to hard connect the intercooler. Still no tach gauge. Original tach with a very tight connection. Tough to get out too.
The white cable of the "RPM box" (?) ties in to the black/purple of the CDI wiring. There is also a black ground and the a red that ties into an existing red/white on the right side of the engine and then a grey wire. The grey and red go to a solenoid switch attached to the WUR that then goes to the cut off valve.

the "rpm box" is an aftermarket module that wont allow your wur to richen up until it exceeds the rpm of the chip you have in it . it opens and closes the vacuum line that controls the boost section of the wur