86.5 No Start – Please Help
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From: Cleveland, MN
86.5 No Start – Please Help
I just put in MMs, OPG and fuel lines.
Also replaced half of the “RPM and Reference Mark Transmitter” connector (sensor half crumbled during fuel line replacement).
MAF is in, Air Box is out.
Jumped FP relay for about 20 seconds. No leaks.
Replaced relay and cranked. No start.
Small shot of starting fluid into MAF yielded one pop.
Removed cap from fuel rail. Jumped relay. Good fuel flow.
Replaced cap, jumped relay and cranked. Two or three pops.
Another small shot of starting fluid, relay still jumped. Started and ran good.
Shut it off after about 20 seconds to check for leaks. No leaks.
Replaced relay and cranked. No start.
Jumped relay and cranked. No start.
Removed cap from fuel rail. Jumped relay. Good fuel flow.
Pulled one plug. Dry as can be.
What did I screw up?
Where do I go next?
All ideas welcome.
Thanks again in advance.
Also replaced half of the “RPM and Reference Mark Transmitter” connector (sensor half crumbled during fuel line replacement).
MAF is in, Air Box is out.
Jumped FP relay for about 20 seconds. No leaks.
Replaced relay and cranked. No start.
Small shot of starting fluid into MAF yielded one pop.
Removed cap from fuel rail. Jumped relay. Good fuel flow.
Replaced cap, jumped relay and cranked. Two or three pops.
Another small shot of starting fluid, relay still jumped. Started and ran good.
Shut it off after about 20 seconds to check for leaks. No leaks.
Replaced relay and cranked. No start.
Jumped relay and cranked. No start.
Removed cap from fuel rail. Jumped relay. Good fuel flow.
Pulled one plug. Dry as can be.
What did I screw up?
Where do I go next?
All ideas welcome.
Thanks again in advance.
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From: Ball Ground, GA
"Also replaced half of the “RPM and Reference Mark Transmitter” connector (sensor half crumbled during fuel line replacement)."
The sensor generates a very low power signal. It takes very little resistance to make it unreliable. The new connector would be my first point of attack.
The sensor generates a very low power signal. It takes very little resistance to make it unreliable. The new connector would be my first point of attack.
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From: New York
Does the tach move when you crank? If it doesn't, I would be looking at the crank sensor and what you did there.
[Wally beat me -- adding] did you bother the injection wiring when in there? Could be brittle and any one of them losing continuity, will stop all from firing.
[Wally beat me -- adding] did you bother the injection wiring when in there? Could be brittle and any one of them losing continuity, will stop all from firing.
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From: Johnson City, TN
There are two groundpoints located under those fuel hoses in the back of the valley. They are mission-critical. One of them is the direct and only ground for a list of cool stuff: O2 Sensor, MAF, LH, EZK, and so on. That is where the electronics and injectors find their grounds, not inside by the CE panel.
Also two that link block to the body at the mount strap for each of the two coils. Again, mission-critical, though it doesn't seem like it.
And I think there is a ground near the front of the car for the final stages under the edge of the front of the hood on the drivers side. But you probably didn't disturb that.
Both above areas, along with the MAF harness wire (fraying beneath boot) can cause intermittent running and no start. And no re-start after a seemingly perfect start.
Tach may still bounce even though the MAF harness wire is shorting. Seen it twice now.
Another place is if you damaged a wire manipulating the boots on the injector plug-ins. A short takes them all out I think. It can be intermittent. Check it by pulling the accessible one near the drivers firewall and hooking up a noid light instead. But do that only after checking and cleaning and tightening all the above.
That's how I'd address the 86.5 after an intake job. If you don't know the status of the above, its really not the efficient approach to try to O-scope and hunt the deviant. Do them all to a confirmed status first, then you could do advanced troubleshooting later if needed.
Mine will run with/without the air temp sensor in the inlet plenum.
Also two that link block to the body at the mount strap for each of the two coils. Again, mission-critical, though it doesn't seem like it.
And I think there is a ground near the front of the car for the final stages under the edge of the front of the hood on the drivers side. But you probably didn't disturb that.
Both above areas, along with the MAF harness wire (fraying beneath boot) can cause intermittent running and no start. And no re-start after a seemingly perfect start.
Tach may still bounce even though the MAF harness wire is shorting. Seen it twice now.
Another place is if you damaged a wire manipulating the boots on the injector plug-ins. A short takes them all out I think. It can be intermittent. Check it by pulling the accessible one near the drivers firewall and hooking up a noid light instead. But do that only after checking and cleaning and tightening all the above.
That's how I'd address the 86.5 after an intake job. If you don't know the status of the above, its really not the efficient approach to try to O-scope and hunt the deviant. Do them all to a confirmed status first, then you could do advanced troubleshooting later if needed.
Mine will run with/without the air temp sensor in the inlet plenum.
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From: Cleveland, MN
Grounds are all good.
Crank sensor works. Got 2 volts AC at sensor connector while cranking.
Don’t know if it makes it to the EZF. Will check that out tonight.
It also appears that there is no spark.
Will a missing crank sensor signal kill both fuel and spark?
Crank sensor works. Got 2 volts AC at sensor connector while cranking.
Don’t know if it makes it to the EZF. Will check that out tonight.
It also appears that there is no spark.
Will a missing crank sensor signal kill both fuel and spark?
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From: New York
I believe it kills both, fp for sure. Safety feature, if no signal from crank (perhaps b/c of crash) Porsche doesn't want fuel being pumped into a possible fire situation. I'm thinking 2 V from the CPS isn't good, but someone else needs to verify.
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From: Cleveland, MN
Had the car running again last night. Jumped the FP relay and gave it a shot of ether and it started. Revs up fine and idles good. Didn’t drive it or even put it in gear. Let it run for about 5 minutes. Temp gauge was at about normal. Shut it off and no restart. What is going on?
When should the FP relay energize? Put a test light in place of its coil and get no light. Ground one side of light and it lights when key is on. There is continuity from one coil connection to pin 17 of LH control connector. Seems there is no ground coming from LH control. What would likely cause this?
All fuses are good. Relays XXV (LH) and XVI (EZF) are good and energize with key on. Crank signal is present at EZF pins 7 and 19. The WSM says >2.5 and it reads about 2.3 with digital meter while cranking the starter. Is this enough? I will check it with a scope in case the meter is too slow or doing some averaging.
Also, how long can the FP relay be jumped without worries?
When should the FP relay energize? Put a test light in place of its coil and get no light. Ground one side of light and it lights when key is on. There is continuity from one coil connection to pin 17 of LH control connector. Seems there is no ground coming from LH control. What would likely cause this?
All fuses are good. Relays XXV (LH) and XVI (EZF) are good and energize with key on. Crank signal is present at EZF pins 7 and 19. The WSM says >2.5 and it reads about 2.3 with digital meter while cranking the starter. Is this enough? I will check it with a scope in case the meter is too slow or doing some averaging.
Also, how long can the FP relay be jumped without worries?
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For the first question, the FP is not energized when the key is on, only when it is cranking. I think it needs to be getting the CPS signal to pump.
In answer to your previous question: Missing CPS signal will kill both fuel and spark. With 'batch firing' all injectors go to ground at the same time (ground from LH) if no CPS, no ground. Also, if there's no ground or weak ground on LH (or from LH) it won't be able to fire the injectors.
You're getting enough fuel flow to keep it running, but not enough to start it on it's own. How long do you try to crank it on its own before giving up? I wonder if the backflow valve is bad and the fuel rails are just dry when you first try to start it. You said when you removed the cap at the fuel rail and jumped the fuel pump you got good fuel flow. You may need to get more info than that. Maybe get a fuel pressure gauge from Roger and install it so you can quantify the actual amount of fuel flow. What seems like 'good fuel flow' may not be enough. Maybe check the vacuum line to the FPR also.
If you're getting no ground signal out of the LH, I'm betting it's not getting a ground IN.
Low voltage at CPS could be caused by bad ground as well. High resistance=lower voltage. Clean ground=less resistance.
You said all grounds are good. Did you go over the grounds at the back of the 'V' and make sure they're good (under the air box)? That's where the MAF and the LH get their ground from.
How is your battery? If it's low it might not have enough amperage to crank the starter and everything else, but once the starter is no longer drawing all that amperage it can power the rest at idle.
In answer to your previous question: Missing CPS signal will kill both fuel and spark. With 'batch firing' all injectors go to ground at the same time (ground from LH) if no CPS, no ground. Also, if there's no ground or weak ground on LH (or from LH) it won't be able to fire the injectors.
You're getting enough fuel flow to keep it running, but not enough to start it on it's own. How long do you try to crank it on its own before giving up? I wonder if the backflow valve is bad and the fuel rails are just dry when you first try to start it. You said when you removed the cap at the fuel rail and jumped the fuel pump you got good fuel flow. You may need to get more info than that. Maybe get a fuel pressure gauge from Roger and install it so you can quantify the actual amount of fuel flow. What seems like 'good fuel flow' may not be enough. Maybe check the vacuum line to the FPR also.
If you're getting no ground signal out of the LH, I'm betting it's not getting a ground IN.
Low voltage at CPS could be caused by bad ground as well. High resistance=lower voltage. Clean ground=less resistance.
You said all grounds are good. Did you go over the grounds at the back of the 'V' and make sure they're good (under the air box)? That's where the MAF and the LH get their ground from.
How is your battery? If it's low it might not have enough amperage to crank the starter and everything else, but once the starter is no longer drawing all that amperage it can power the rest at idle.
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From: Cleveland, MN
The grounds at the back of the “V” are good. I had them loose, cleaned them, inspected and tightened them when I changed the fuel lines. There is continuity from EZF pin 12 to ground and LH pins 5 and 11 to ground. The battery was new last year hand has full charge. Battery positive and ground strap are clean and tight. The car ran fine and started great before I replaced fuel lines. I’m suspecting I caused some sort of electrical issue, especially since I get no power to the FP relay coil, but the question of what and where remains.
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From: Cleveland, MN
By grounds at the back of the “V” I assume you mean MP VII and MP IX.
They look good and are tight but I suppose there could be corrosion in the crimp even though things were fine before replacing fuel lines. Perhaps moving them around somehow degraded the connection without completely interrupting it. Guess I’ll pull them back off and investigate even though it’s a bit of a PITA as you really can’t get at them without removing fuel lines.
They look good and are tight but I suppose there could be corrosion in the crimp even though things were fine before replacing fuel lines. Perhaps moving them around somehow degraded the connection without completely interrupting it. Guess I’ll pull them back off and investigate even though it’s a bit of a PITA as you really can’t get at them without removing fuel lines.
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From: Cambridge England
Check temp sensor 2. If the LH ECU thinks the signal is implausible i.e. short or open, the LH will default to normal temperature fuelling. So this will result in too weak a mixture to start the car easily from cold.
Peel back the rubber boot on the sensor, check the wires aren't shorted, and the pins look clean. Then check that the body of temp 2 sensor is a very low resistance ground to the engine block. (recent thread here on this last one)
Peel back the rubber boot on the sensor, check the wires aren't shorted, and the pins look clean. Then check that the body of temp 2 sensor is a very low resistance ground to the engine block. (recent thread here on this last one)