911Ragtop

jvandyke

I think a new starter might be less susceptible to the issue but we also swapped starters, problem went a way for a while, than came back and DESTROYED the starter, the kick back shattered the planetary gears. We put the old starter back in and went back to 50% kick back clunk. This starter is slated for replacement too as the nose piece is wallowed out badly, I added a bushing that has since been destroyed so nothing for it but another new one. Save your receipt!!! If your sensor wires are long, be sure they're routed as far away from the starter as possible, don't let them loop toward the left side of the engine but up and away as quickly as possible. We reinstalled the bell housing last night and need to do the sensor brackets and all those fun bits next.

Pin It

I've had the same issue with my early build '87 n/a (Nov '86 build date). I'm now on my 3rd starter in just over a year of ownership. According to my records, the previous owner was having the same problem in the first 3 months of ownership at 1,800 miles. The dealer installed the updated reference sensor bracket at that time, but the car has been through way too many starters for 65,000 miles. Each time I replace the starter, the problem becomes less frequent, but seems to revert to happening every 7 or 8 times I start the car.

I would be very interested in a fix that doesn't involve replacing the starter every 6 months.

jvandyke

What about another shield bolted to the starter itself, like a heat shield.
OR this
​​​​​​​https://www.ebay.com/itm/Porsche-Hig...-/261157376960

John_AZ

Over the past 6 1/2 years since I originally posted (), I have also had a recurrence a few times. My '87 does not have the reference sensor cutout in the bell housing. I have swapped starters with new rebuilt. I cleaned the 2 wire starter connection behind the brake booster (top). My current fix that has helped a slight starter kickback----now very seldom--is to use a midrange gas octane for every other fill up. Mixed with the remaining tank gas. ( I do not run premium). I have also increased the RPM to the 1000 mark at idle by use of the throttle body idle screw---not the throttle cable adjustment screw.
Another possibility of kickback is to let the car idle for a few seconds after a drive to clear the intake.
GL
J_AZ

951and944S

Problem is unshielded/sleeved timing sensor.
Resolution for crank position is worse when cranking and spark fires at wrong crank position, kicking back against engaged starter teeth.

Check that timing/reference sensors have the additional aluminum sleeve.

T

Tom M'Guinn

Also, the strength (amplitude) of the speed/ref pulse is a function of speed, so keeping the battery on a tender and fully topped-off really seems to help, since the motor is cranking faster and the sensors are producing stronger pulses.

951and944S

True.

Had a race car with this problem, starter kickback was so violent, I thought when the problem would arise, the bell housing would actually shear and leave us DNFd out of town and far from home.

I carry alot of parts, and have done a clutch on site at Sebring once but a bell housing swap was not something I wanted to do if it could be avoided.

Got the car home and experimented, installed aluminum sleeves around the sensors and never had the problem again.

Don't know how you could measure for it, but I don't think it's unreasonable to assume that a measurable current is present at the ring gear, transferred through the starter drive from the armature and/or the solenoid, through the fork and along the same path.

T

Tom M'Guinn

Argues for big, short, clean ground straps in the area....

Phaedra

Glad I found this thread, not so glad I actually need it :-)
I've been having some problems with backfire into the inlet on my 1987 944S.
First time was a couple of years ago. I tried to tart the car, heard a very loud bang (firecracker sound), and something fell to the floor. It appeared to be a small sort of lid (round, 63mm diameter, 4mm thickness) that was blown out of the bottom of the inlet collector. It was really scary, since I heard a loud bang, and some smoke was coming out form under the hood (oily smoke).
We inspected the cams, timing, ignition, etc. but couldn't fond anything wrong at all. Using some JB Weld, I glued the part back into the inlet collector, and the car started perfectly normal after that.
Afraid of getting the same blowout again, I always pushed the throttle in just a little while cranking, but this caused very hard starting from time to time (probably due to the fact that the idle switch wasn't pushed in?).
Ad so I stopped doing that. The car always started "at first click" ever since. Until a couple of days ago. Same thing. Loud bang. Something falling to the floor. Heavy sigh. Glue the thing back in, car starts again (now with quite a bit of hesitation, but I did push the throttle again a little bit, just to prevent this behavior again).
I'm not sure that I'm experiencing the same thing as you guys, it's not just a pinging, this is next level.
I'm wondering how starter interference could cause something like this? I will try to make some pictures of the sensor bracket that is installed on my car, and of the starter, to get an idea if this could be a possibility even.
Maybe I should pull the injectors, as someone on another forum already suggested (but I discarded that possibility too soon)? I have no idea how easy or hard it is to pull the injectors, but I'm getting tired of being afraid to start this wonderful car.
Once started, though, it runs perfectly at every rpm, and it pulls nicely (above 4K rpm, that is). I do have some sort of exhaust leak somewhere near the collector, I suspect, judging from the sound it makes. That makes it run a bit rich, if I'm right.
Thanks for any input,

Phaedra

Phaedra

This is the best I could do with my camera to try and get a picture of the sensor that is now installed...

jvandyke

another blown up starter, none slotted bell housing, shielded sensor and still get kick back resulting in 3 broken starters, thoughts? We may have other issues (leaky injector?) but this is really crazy, BTW these are all the "correct" fatty starter

911Ragtop

When you say leaky injector why do you think that because of a misfire? Does the car run on when it is started? My thoughts are if you have 30 year old fuel damper or regulator that might cause some issues. At one time on my 944 which was purchased as a non runner I assumed I had a leaky fuel injector when I finally figured out it was a bad fuel damper. I discovered this because I took the throttle body off and had about an inch or more of gas in the bottom of the intake (air) manifold and wondered how the heck did it get in there. So I did a little inspecting and found if I turned the car over and pulled the vacuum line off the fuel pressure damper it was getting gas in it. Same as the fuel pressure regulator gas in the vacuum line. So I replaced both and and the car ran very well.
So basically I can’t say that this is what’s happening with yours but it’s worth pulling the vacuum lines off after trying to start and smelling them for gasoline. If it’s bucking that’s kind of what happened to mine when that was going on.
Testing leaky injectors isn’t fun but it can be done just be super careful. You have to pull the fuel rail up and I put a jumper wire on the dme relay and you need to put the injectors in glass coke bottles (I actually took four spice jars out of my wife’s collection and used them. She’s probably wondering where her nutmeg went but who cares I got my Porsche running...) and turn the key to get the fuel pump to run and then check for leaks. While you are at it it’s possible to check spray pattern and quantity. I could see the spray from the drivers seat with the hood up. You have to be super careful in this situation to avoid sparks and you need to disconnect the coil wire. I like working on my car but I don’t like fuel stuff for two reasons because it smells and it makes me dizzy and it’s super dangerous. I always keep a garden hose around and a couple fire extinguishers.
To solve the original reason for this post on my brothers 944s we just took a trip to Autozone and got an off the shelf started and it took care if it no problem.
Could it be the heavy duty starters are overkill?

911Ragtop

good point. I had that problem too and yes turn it over and then pull the vacuum lines off the fuel pressure regulator and the fuel pressure damper. (Be careful if there’s fuel in there it can splatter you) I had to replace both on my 944 which was a non runner and those two items were the ticket to getting it to run again. I did have a bucking problem occasionally on startup too.

Pulling the vacuum lines is an is an easy check. ( It helps to put a flat head screw driver behind the hose to push them out rather than just yanking on them) If you do have gas in the vacuum line ms you will have to pull the throttle body off and dry out the air intake manifold. I was able to shove rolled up paper towels in mine and pull them out wet with gas but I got it out.

jvandyke

I say leaky injector because we also had hot restart issues last fall before putting the car up for winter. It would fire up nice stone cold but the rest of the day restarts required far more cranking then it should, so I thought maybe an injector was leaking down causing flooding/richness that took the car a bit to over come on restarts, but this residual fuel would dissipate overnight. I did the injector test last year and did NOT see anything amiss. Now you mention the FPD and FPR. We replaced the FPR early in the game but the dampener was bad and we bypassed it (as is fairly common I found out). So it's been running without one for quite a while. I'll look into testing the regulator's vac line for fuel and possibly restoring the dampener (but they are stupid pricey).
I'm not sure this is related to the starter kickback and subsequent destruction though.
If the starter is generating an electric field that triggers the sensor and tries to fire the car "early" (and "backwards") this kicks against the starter which is still trying to spin the engine correctly, you get violence and mahyem; busted starters. This makes sense to me but using the right bell housing, correct starter, good grounds, shielded sensors "should" elimnate that UNLESS extra fuel hanging out allows the "backfire" where as without this fuel it would not backfire so readily.
If this makes sense I will look hard at fuel leaking in somewhere. That's the plan at the moment; another new starter and fuel leak possibilities from regulator. The dampener not being involved should probably not be an issue, I don't think, or if so I can plumb one back in, although I'm not too keen on all that work unless it's highly suspect.
I will look hard at the regulator and leak through first. As I recall from previous work it makes and holds good pressure while running but tended to loose it a bit faster than it should, dropping in pressure after 20 minutes or so which is a bit too fast as I recall (and prompted the injector test).
Do we think extra fuel exacerbates the tendency to backfire and destroy starters?
Thanks for the input.
I'm leaning toward keeping this car personally. I really like it. I'm pretty sure mamma will have a cow though.