Bucko74

All,

Got stuck into the EZF/LH test plan last night from John Speake. This is what I have found so far.

All grounds in good order
All plugs in good condition, cleaned contacts on a few.
Checked spark with a timing light - nothing.
Checked power to LH and EZF relays - good (actually heard them clicking in too)
No signal to Fuel pump relay, but runs when jumped.
Checked plugs on EZF and LH units - good condition, no sign of damage or corrosion.
Tested power between pins 25 and 12 on EZF plug with ignition on and all good (battery voltage.
Tacho does not move at all when cranking.

I dont have a scope so cant test the CPS, but everything seems to be pointing to this. HOWEVER, I read today in a post that a fauly rev counter signal (break or short) can affect the signal from the CPS (by leaking voltage).

Any thoughts on next step other than replace CPS. Can anyone tell me how the rev counter fits into the circuit and where to trace for a short?

Ive read horror stories about CPS removal...............dont really want to go there if I dont have to...

John Speake

The EZ-F ECU does sometimes fail to synchronise with the teeth and gap on the flywheel.

So your EZ-F may be faulty. Can you get someone to test it in their car ?

Bucko74

only person I know who has a 928 Euro locally is my mechanic, so I guess I'll ask him.

John, if the EZF is screwed, would changing the chip out make a difference. Obviously thats an open question, but I do have the EPROM I bought from you for both LH and EZF I haven't got around to fitting. Guess it couldn't hurt to try.

Think I'll change out the CPS and see if that does the trick, then I'll take the EZF out and see if I can get it tested.

Thanks for you help.

John Speake

Changing the chip won't help, unfortunately :-(

Bucko74

So just an update on other stuff I've been looking at whilst waiting on a CPS from Roger.

1. I had heard that a fault or short in the signal to the tacho can sometimes affect the signal from the CPS to the EZF (by leaking voltage) where the signal is not strong enough and EZF does not register. So I traced the Tacho circuit back to G7 on CEP, and temporarily disconnected it. No Change - still NO START. Did I get the correct wire?

2. Pulled the CEP to give it a cleanup and notice wire O-8 in a terrible condition. outside coating was melted and burnt from the plug O to where the harness disappears into the firewall. From the WD, traced this to pin 1 on the 14pin connector. Checked continuity from CEP to pin1 - all good got 0.8Ohms. Checked line to ground and there was no circuit so it has not shorted to ground any where. But I cant tell if its melted any other wires on the hardness and shorted to them. Pin1 goes to terminal 61 on the alternator - would a short or break to this cause a NO START. My logic says no, unless it affected the spark ignition (which there is none) - Anybody know if this is possible.





3. In removing the EZF brain, notice the part number printed on the back is 928 618 124 00, but the CEP lists this part number for 84 as 928 681 124 03/04. Have I got a replacement unit in my car and is it correct????

Any help with the above would be appreciated.

Hopefully clean the CEP this weekend and reinstall, notice a number of heavily corroded blades on the plug receptacles. Will be nice to eliminate something simple with a cleanup.

Landseer

Best get a cps on order from roger.

Replace bosch sensors preemptively on 32 year old cars
To not do so prior to troubleshooting is stupid.

Mine have failed intermittently in some cases, in others completely. 84 euro needs another now. 86 got two during 8 years, first one preemptively, second one after intermittent stalls out followed by complete falure.. 85 got one. 86 951 needed one, it completely failed. 86 944 had an failed one. New to me 86 928 suffered intermittent stalls with previous owner, then since previous owner replaced cps it has been reliable.

Bucko74

Thanks, seems to be concensus to change CPS out before I do anything else.

Bucko74

SUCCESS!!

Received the CPS from Roger (in record speed I might add - 5 working days from Texas to Perth, Western Australia!!).

After wrestling with the lack of room, I ended up removing the fuel lines to get a better bite at the existing CPS, but it came out reasonable easy with some fencing wire and 14inch screwdriver as the lever. Slid the new sensor in and put it all back together. Manually ran the fuel pump to check for leaks...topped up the coolant, then turned her over and she fired up straight away!!!!

Oh the rumble was well worth all the pain and skin lost. Immediately took her out into the chilly night for a well overdue re-acquaintance...

A big thanks to everyone who chimed in on this thread and all the other threads I've read. Particularly John Speake from JDS who sent me a copy of the Porsche EZF/LH test plan. Appreciate the help provided to this novice mechanic...

Now onto the next job - transmission leak..........