help please

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30 Mar 2013 13:24 #14122 by skipper928
help please was created by skipper928
I have begun to work on my 928, just got a battery to see what it does. I noticed that when i turn the motor over. That the speedo jumps around a good bit. The man that sold me the car says that it needs the fuel injection computer. Can anyone help me diagnose this so that i can enjoy the drive.thank you.

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30 Mar 2013 15:53 #14127 by Kiln_Red
Replied by Kiln_Red on topic help please
Skipper,
We need more info. Model year and ROW/US would be helpful. Also, some history on the car would be great. Has it been sitting up? What maintenance has been done?

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30 Mar 2013 20:20 #14140 by mm928
Replied by mm928 on topic help please
Does the speedo jump around but the RPMs do not or both etc.....

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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31 Mar 2013 06:52 #14146 by skipper928
Replied by skipper928 on topic help please
The car has been sitting for a little more than a year. It's an 1981 with a 4.5, i have no real maintenance records. The fluids look good,it has 77,000 on the clock. I don't know what relays or what fuses do what i don't see where that a labeled.

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31 Mar 2013 07:04 #14147 by skipper928
Replied by skipper928 on topic help please
The car has been sitting about a year.i don't know much about the maintenance history. Its an 1981 us spec. It turns over and sounds like it has compression. Their is fire

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31 Mar 2013 12:14 #14152 by Kiln_Red
Replied by Kiln_Red on topic help please
Skipper, you need to go to 928gt.com and print off the fuse/relay chart for your car to keep as a reference. Better yet, you should contact Roger at 928sRus and order the Jim Morehouse CD collection. That will be the best $70 you ever spend on your 928. Virtually all of the tech information concerning the 928 is on that CD set.

Open your gas gap. Can you smell varnished fuel? If yes, then you have a lot of work to do to prepare the car to run again. If you're unsure, spray a mist of starting fluid into the intake and start the car. If it responds to the starting fluid, then you have a definite fuel issue. If not, then you must confirm spark and compression.

See if the car responds to starting fluid and report back.

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31 Mar 2013 14:43 #14157 by skipper928
Replied by skipper928 on topic help please
I did that with a bit of gas in a spray bottle, it tried to run but i couldn't keep the spraying up to get it to fire over completly. It seems like it wants to run. How much noise does the fuel pump make when you turn on the key.

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31 Mar 2013 15:27 #14160 by Kiln_Red
Replied by Kiln_Red on topic help please
Your car has an L-Jetronic fuel injection system, so the fuel pump doesn't run when the key is turned to the ON postition. It only runs after the starter is engaged. Have a helper kneel at the rear of the car while you try to start the car. Also, you should hear the pump continue to run for a moment after the starter is disengaged if a helper is not available.

Or...

You can remove the ball cup from the end of the passenger fuel rail. Be careful not to lose the ball. Fit a water bottle, or something similar, over the end of the rail and roll the starter over for a few seconds. If there was fuel in the tank and the pump were running, then you will have fuel in the cup unless a fuel line were collapsed or blocked (not at all likely).

Is the fuel gauge working or is it stuck at one level?

Try this and report back when you have confirmed whether or not the pump is good or not.

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02 Apr 2013 23:01 #14219 by xstepson
Replied by xstepson on topic help please
Austin,
I thought that all the 928's fuel pump ran for 3 seconds with the key first turned to the on position, but after that, the starter being engaged or the engine running was necessary for continued fuel pump operation. Am I mistaken?

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03 Apr 2013 08:55 #14220 by Ducman82
Replied by Ducman82 on topic help please
^^^^ that is correct. the pump should make a "priming" noise when the key is turned to the IGN hot, before cranking. thens stops. starts back up when the starter engages.

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03 Apr 2013 09:10 #14221 by Kiln_Red
Replied by Kiln_Red on topic help please

Austin,
I thought that all the 928's fuel pump ran for 3 seconds with the key first turned to the on position, but after that, the starter being engaged or the engine running was necessary for continued fuel pump operation. Am I mistaken?

^^^^ that is correct. the pump should make a "priming" noise when the key is turned to the IGN hot, before cranking. thens stops. starts back up when the starter engages.


Not so on L-jet, LH 2.2, or LH 2.3..

If you want to see for yourself, open up the passenger fuel rail. Place something there to catch fuel and turn the key to ON. Look and see how much fuel is collected.

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03 Apr 2013 11:26 #14222 by wallyp
Replied by wallyp on topic help please
The earlier cars with the expensive fuel pump relay that contains an electronic circuit do run the pump briefly when the key is turned on, and then run the pump when the circuit sees ignition pulses.

The later cars with the standard "53" relay run the pump only when commanded by the ECU, based upon ignition signals.

This often means that the earlier cars may fire just a little bit sooner, as the later cars may need a few engine turns to build fuel pressure, while the early cars start building fuel pressure even before the engine turns.

Wally Plumley
928 Specialists
www.928gt.com

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03 Apr 2013 11:41 #14224 by Kiln_Red
Replied by Kiln_Red on topic help please
While the relay is the same between CIS and AFC, the ECU is not. The L-jet ECU won't allow the pump to energize in advance of starter engagement.

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04 Apr 2013 00:21 #14237 by xstepson
Replied by xstepson on topic help please
Austin,
Since I no longer have an L-Jet car, I'll just have to wait until this weekend to see other's cars to test you on this. :)

(You have gotten me really curious on this now!)
:)

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