924Board.org

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

I am lost. Been trying to get my 924 NA (1982) running again for over a year, with no success and am trying to save up extra cash for a real Bosch mechanic. The car has no spark and no fuel. the following has been done:

A. Dizzy rebuilt by a Bosche certified shop. Correctly indexed it and the rotor pointed just before cylinder 1.
B. The ignition switch has been replaced with a new one.
C. The ignition module has been replaced with a new one.
D. The wires from the coil to the fuel pump relay have been replaced.
E. The wire from the coil to the ignition module has been replaced.
F. The EIS has been bypassed per the FSM
G. Battery has a full charge
H. Getting 12 volts on both sides of coil to ground.
I. Getting 12 volts to terminal 4 on the ignition module
J last time I checked which was a while ago bypassing the relay gives me fuel per the FSM but no spark.
K. Fuel pump relay bought new and replaced.

Any ideas would help.
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1982 Porsche N/A

Ozzie · Posted: Sun Nov 07, 2010 7:12 am Post subject:

terminal 15 of the ignition module should get power when cranking and ign on. Ok - 4 for ox sensor- sorry.

Try 12volt off the battery to the coil direct
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

joejax · Posted: Sun Nov 07, 2010 11:19 pm Post subject:

Bad grounds maybe? I added another ground from the motor to frame and it seemed to make difference.
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I got nothin'
Uhhh...you got any pics?

Paul · Posted: Mon Nov 08, 2010 3:47 am Post subject:

This type of problem can usually be resolved by following the test procedures in the factory service manual.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Feltron · Joined: 11 Jul 2010 Posts: 44 Location: Port Murray NJ

Does the fuel pump run and the gas just isn't getting to the motor or when the key is on is the fuel pump off?

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

The only time I can get the fuel pump to run is bypassing the relay per the FSM and Haynes. Right now am suspecting a timing issue and intend to check that out again. But I dobt that will correct the no fire no fuel syndrome.
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1982 Porsche N/A

Ozzie · Posted: Thu Nov 11, 2010 9:09 pm Post subject:

do you have continuity from 1 on the FPR to the 16 (or 6) on the TIU?
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

staticsan · Joined: 19 Jan 2009 Posts: 450 Location: Sydney, Australia

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

That wire was replaced. It failed the Ohm test specified by the FSM. It goes from the coil to the relay per the Haynes and FSM electrical diagrams. I'll have to do some research on the TAI unit and the TIU. As I do not know what they are as of yet and if I have them.
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1982 Porsche N/A

staticsan · Joined: 19 Jan 2009 Posts: 450 Location: Sydney, Australia

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

Thanks for the clarification Wade. The unit (ignition module) was replaced with a new one during initial troubleshooting. Wires to it were tested/replaced/repaired per the FSM. Tomorrow if I am not lazy from working the night shift, I am going to take a look at the timing again. For a sec, got a quick squirt of fuel while messing with the dizzy.
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1982 Porsche N/A

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

Out of curiosity I ran a jumper wire from the battery to the negative side of the coil. Viola had a strong fuel flow, but no spark. How can this info help me out? Re-stabbed the dizzy on cylinder 1 indexed it, and lined up cylinder 1 o the dizzy and verified it is on TDC also.
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1982 Porsche N/A

PeterW · Joined: 17 Dec 2003 Posts: 78 Location: Auburn WA

[quote="oldmanwintersret"]

H. Getting 12 volts on both sides of coil to ground.

Any ideas would help.[/quote]

Well... I'm not a mechanic, but this could indicate a number of things. My understanding is that one of the leads of the coil SHOULD be grounded - if it reads 12 volts on both sides, it's not. This would lead me to think:

A) The coil is internally shorted and should be replaced. Potential damage to other circuits. Easy swap.

B) The ballast resistor is bad/open/disconnected and not closing the circuit. This is supported by the fact that when you grounded the coil, other things started to work.

Since you have checked/changed the transistor module and wiring (you did put the ballast resistor back in I assume) I would check the other ballast resistor (IIRC 1.5 Ohm, not 1.0 Ohm) and see if you have a complete circuit.
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1980 931

oldmanwintersret · Joined: 06 Apr 2009 Posts: 133 Location: San Antonio, Texas

From what I understand from the FSM if I am reading it correctly terminals 1 and 15 on the coil to a ground should read 12 volts with the key on. Resistance between 1 and 15 are 0.62 which is acceptable.Voltage on H+ and H - are 11 volts. The only thing I can see is that the timing might be still off, even though it is indexed correctly.
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1982 Porsche N/A

PeterW · Joined: 17 Dec 2003 Posts: 78 Location: Auburn WA

Sure - but I don't think that isolates the fault. Divide and Conquer.

There should be 2 wires on 15. One should measure 1 ohm to pin 4 of Ignition box - you said that you checked this, and I bet you have 6 or 8 times at least, so I buy that.

The other should lead to the starter solenoid assuming that I'm looking at the correct diagram here. It needs a 1.5 Ohm ballast resistor. This looks to be the wire you replaced, which makes sense. If there was a short to the high voltage side internal to the coil, it may have taken this resistance wire component out. You fixed a fault that was caused by? Was the resistance too high before you changed it? It's possible that the coil short caused the resistance wire to fail on you.

It looks to me as though there is only 3 components in the circuit - the coil, the transistor box, and the ballast resistors. When you don't have a drop in voltage, you don't have current flow per ohms law. Yea, I know, there is a low duty cycle pulsing that you can see with a scope, but if you have a shorted coil you won't get any High Voltage even if the primary side measured correctly. (At DC it's shorted anyway, so measuring the resistance doesn't tell you if the short exists, only that it has not gone open. A short between the HV side and the Primary does not change the DC value, only the effective turns ratio, which will prevent the coil from providing a High Voltage.)

The only other test that I can suggest, without changing components, is to get an "In line Spark Plug Tester" - it's a little light that has a fits between the plug boot and the spark plug, and lets you see that you actually have a high voltage. Search Amazon and they have them for under $10. I saw them at Autozone for $4 on sale. You can screw with the dizzy all day, if you don't have HV you don't have spark. It has been worth the $4 for me to have the tool.

Now, I'm not saying that I'm 100 percent certain on this car mechanics stuff, and clearly if you don't have fuel it won't fire either, but the transformer stuff I do know.
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1980 931