IMB951

Hey guys,

My 89 has been running quite well up until now since installing the 951 MAX chips and tuning the MAFterburner appropriately. The car holds boosts strong and I usually get 15psi by ~3500rpm. AFRs have been spot on with low 11s and high 10s on boost and low 14s at idle and part throttle 4th and 5th gear cruising.

For a few months the car has had an intermittent no-spark startup on cold and warm starts. I keep a DME jumper at all times and each time I get no spark I'm jumping the DME relay and confirming that it's getting fuel, and it turns over and doesn't fire. I've gotten the car to fire each time by either pushing down firmly on the boot on top of the Bosch (likely OEM) coil, or completely removing the wire coming from the coil to the distributor and replacing it. I get a confirming "click" when pushing the wire into the distributor, but not when I push down on the coil. I've checked inside the boot to confirm the presence and condition of the metal leads on the wire that go into both the distributor and coil, they look fine. Battery is also good and is usually maintained by a float charger. Starter cranks quickly and car turns over with ease.

Up until tonight, the car has run great, boosted at 18psi last winter and 15psi this spring and summer with good AFRs. Took the car out for a spirited run last night after it started without issue and it ran great and I gave it plenty of cool down time.

Tonight, my 951 didn't want to spark again when I started it the first time. Naturally I go right ahead and jumper the DME to be sure fuel is being delivered and is pressurizing, and try again. No spark. Go right back and push down on the plug wire on top of the coil. No spark. Go back and pull the wire off the coil and the distributor, look at it, put it back on, confirming they (and the rest of the plug wires) are snug. I get spark and the car starts and I'm on my way after a brief warm-up.

I wasn't on a glory run tonight and just wanted to enjoy the twilight air temps on the highway, but the car was sluggish at first once getting to operating temps, so I made a couple 4th gear pulls and the car did NOT want to build boost and was VERY hesitant around 4000rpm. It only got more pronounced two or three other times I went WOT. Turned back around and decided to limp home and stay off the boost. In both 4th and 5th gear with very light throttle my wideband gauge was reading consistently in the 10s and 11s. I saw 10.1 once in 5th gear just cruising. Once off the highway at idle and while putzing home it was running at the same obscenely rich AFRs...

My first guess would be to try swapping coils? The car has newish NGK-BPR7ES plugs gapped appropriately so I have strong doubts about the spark plugs being bad. Plug wires are magnacore reds.

Any suggestions?

Black51

How old is the coil? What about the wires? It would be nice if you could borrow a known good coil first before spending money on one only to realize the coil isn't the problem. I think I would look into the coil though, given your diagnosis.

IMB951

Not sure how old the coil is and the wires are probably 5 years old. Before anyone asks, I always remove the DME jumper after I get the car running and I put the un-jumped relay back in before I hit the road.

67King

Do you know for sure it isn't getting spark, or are you assuming that? In other words, when it does this, have you done anything to check and see if it is getting a spark?

If that is what is going on, get a 12V LED and hook it up to the coil, to see if your coil is being signalled to generate a spark. Could be the alarm, the DME, or the KLR if it isn't. Here's a good thread that helped me find all kinds of problems with my 89 when I first tried to get it running: https://rennlist.com/forums/944-turb...f-options.html

fast951

You may have 2 different issues. One of them (rich under boost) may be caused by a boost leak. A intake system pressure test will solve this one.

The no-start can have many causes. Give us a bit more information...

IMB951

Harry & John,

Thanks for the suggestions. I'll report back this weekend when I have a chance to get it on Dad's lift and look her up & down. He thinks he's got a spare coil to try out also.

John, to clarify, the last time I drove the car it was rich (low 10s) at idle and cruising in 5th after going from hesitant to flat out refusing to pull like it should at WOT over about 5 pulls. The car was seemingly (according to my wideband gauge) delivering fuel while cruising in 5th part throttle and at idle as if it were boosting at WOT.

IMB951

Would a bad coil, or coil that is going bad cause the car to run rich like that at idle and part throttle? Not enough spark, thus the excess (unburnt) fuel would report on the wideband gauge?

Black51

If there is not enough spark to ignite the entire mixture, then yes, the wideband will be seeing a rich mixture. I had an alternator failure a while back. As the voltage went down, the car became less and less powerful, especially under boost. Also, when letting off the throttle, the exhaust would pop a lot with unburnt fuel igniting in the exhaust. I could smell the rich exhaust... Does that sound at all like your car?

IMB951

My car has a LR 4 inch exhaust with no cat so it pops/grumbles pretty frequently even when it's not misbehaving. I will definitely be observing everything closely on the 25 mile drive to the shop on Sunday. Thanks Black51 for that possibility to look into. It sounds very plausible next to the coil possibly being bad. A dying alternator could also impede healthy spark when starting/driving the car...

Here's to hoping it's just the coil or something stupid. Probably won't be, I must remember it's an old Porsche

Will report back...

86 951 Driver

Do you have a spark tester? If not get one. You can hook it in between the plug wire and plug to see if you are getting a spark. If you are then you know it must be something else. They are like $10 at a autozone.

IMB951

Got the car to the shop today. Still misbehaving and stuttering as soon as the boost gauge goes positive. Making good vacuum at idle. Wideband is still reporting crazy rich (10:1) at part throttle just cruising. Here's a quick video so you can hear it stutter on boost in 4th gear:

[youtube]wPp9Wg2JcE0[/youtube]

One thing the video doesn't show clearly is the voltage gauge on the cluster reading at just above the 2nd from the bottom notch, the one marked 12v. Is this too low and should that indicate the alternator is bad?

The car is in the garage cooling off right now. Going to start by swapping the coil and lead wire from the coil to the rotor for good spares and then taking it out to see if it's still doing it. Process of elimination...

Tom M'Guinn

10 volts is too low if everything is working right. Should be high 13's. Low voltage may be causing weak spark? Does the starter crank normally or is it getting slower and slower? If you don't have the tools, you can always get the battery and alternator tested at one of the national auto parts stores.

Black51

That reminds me of when my alternator went...

The boost came on slower and slower as the voltage went down and down. Eventually, boost made the car die as the spark couldn't ignite the extra mix.

Black51

It's tough to see, but does the needle 'flicker' when under boost, when the you hear the popping?

IMB951

Okay, just swapped the coil for a known good one and the car cranked quickly and started right up. I must correct myself in that last post as the voltage gauge was reading a good bit above the second notch, which is marked 12v, not 10 like I originally said. Just edited the post for clarity. AFRs are still obscenely rich at part-throttle.

The car still sputters like in the video I took earlier and doesn't want to boost at all. I think I need to check the car in for an extended stay at the shop and test/swap the alternator amongst other things. Oil from lower balance shaft housing and bottom of turbo's cold side housing. Awesome. Can't wait to look inside the IC pipes.