Landseer

Hi everybody,

I need a little help. 84 seems to have very weak spark, and intermittent spark, evidenced at #1plug, grounded against cross brace. What might cause this?

Background. Got this car 2 months ago, titled on 9/27, had immediate water pump failure within 20 miles of ownership. PO is a 911 owner who bought this from a used car dealer in 2001 and drove it around town infrequently but never tackled maintenance. I drove it home carefully, it was running strong. Been in dry basement garage on jackstands ever since. We are turning it over for first time after TB/WP/MM/OPG and a whole lot of suspension & brake refurb. We tried to be careful and disturb as little as possible in the electrical system during this endeavor, especially green wire. Discovered burned wires in headlamp harness, but think this is not related.

This morning, jiggled some of the relays associated with fuel pump. Have a clear, strong gasoline smell when making our 10 or so attempts at starting, though #1 plug was not wet.

Had one or two bumps of at least one cylinder igniting when checking for spark with #1 plug out. But nothing more.

Checked timing. Confirmed approximate rotor location relative to #1 plug (right,passenger side, front plug) when back notches of timing gears align to cam cover marks at which time crank is at 0 degrees --- seems we got that part right.

Have read archived posts last night and this morning, looking for clues. Have a cheap meter, but haven't started measuring yet. Frankly, not sure where to start

Can you guys provide some troubleshooting pathways off top of head ? Why weak spark? Why intermittent?

Also, I have no idea yet how the alarm feature works and if its connected. Would alarm have any disabling effect on ignition?

Any help would be appreciated. Love this car, really want to get it going.

ZEUS+

Check the green wire, famous for ignition problems.
http://www.mailordercentral.com/928i...602%20907%2000

JHowell37

Burned wires in the headlights most likely mean someone installed high powered bulb/lights at some point. Does it have H4 head lights?

The spark could be weak for a number of reasons. It could be a coil issue (but you almost never hear of that.) I would check the wires that feed the coils. But the first thing I would check are the 7 (or is it 8?) main ground points on the car. 23 years of dirt and corrosion can affect them.

I think the alarm disables the ignition on the '84 models but I'm not sure. There are some posts about the alarm if you search. There is a way to disable the alarm and remove the control unit with a jumper. Mine is like that like but I can't remember which terminals require the jumper wire. If you have spark (even weak and intermittent) then I don't think the alarm is interfering. Start checking grounds and cleaning connections.

Mrmerlin

Start with the simple stuff. First, check the battery connections and clean all of them ,then leave the battery disconnected and on a charger while you proceed.
Next check the ground wires for the engine on the bottom of the engine to chassis under the right exhaust manifold, and at the coil and see if there are grounds that attach to the coil to engine.
Remove the hot post connection and clean it, as well as the 14 pin connector, use an eraser to do this.
Check the connector under the crossbrace for the brain near the hot post. Remove the coil connections and clean them, and make sure the Hi tension wires are all completly seated. As mentioned earlier if your GREEN wire is cracked or worn it would be a great time to replace it, also check its connections at the distributor for the correct firing order, and make sure that the small cut on the body of the dist. is in alignment with the rotor at TDC, the cap needs to be off to do this.

Check the CE panel grounds and pull every fuse and look for corrosion if you find any then it is a safe bet that the lower blower box needs to be resealed, also pull every relay and check for the correct part number and also look for corrosion. Thats a start ........ and its pretty simple stuff

Landseer

Thanks for the cliff notes, will move forward with this. Did Merlin's 1+2. Am questioning my fuel pump now as well. What is the 14 pin connector --- or better yet, where? Sorry to sound so green, but am.

Will work thru methodically. Maybe I'll learn something that I can add-back to the forum.

Thanks again. BTW, used your method of bleed-system, install clutch hydraulics intact, Mr. Merlin. Works. Nice, Thks.

Chris (and wife Laurie and a group of 20's boys and girls trying to revive this shark)

Mrmerlin

the 14 pin connector is tied into the hot post lug once you remove the 11mm bolt then the hot post wires will be loose then you will be able disconnect the brown connector that the hot post wire is wrapped around. as a side not get some heat shrink and put it onto the thick wire with the somwhat whitish insulation , the insulation used to be red. anyway shrink it as well the 2 wires that go foward from the hot post. the thick wire is spun around the 14 pin connector wires 1 time before connecting to the hot post.. The hot post is just in front of the right side front shock tower

Landseer

Not running yet. Car turns over, weak spark, intermittent. Cleaned 14 pin. Charged battery again while disconnected from car. No fuel pump running., though we had it briefly yesterday.

Inspection of CE box showed evidence of corrosion of fuses and contacts. Cleaned what I thought were the pertinent ones to the starting task.

Noted some burned wires at two plug-ins. One really bad brown, with collateral damage to others. Have pics, will show if that might help anybody who cares to try to help.

Removed Z harness and bridged Z terminals ID'd by Alan (from thread search) to ensure alarm is not a factor. Still here no fuel pump.

Checked number 8 injector plug. With ignition on, have 12 volts between each connector and ground. Have continuity between each wire and ground also. Dang.
Might have disturbed various injector plugs, but didn't think so.... Anybody know which CE plug is supposed to supply injector harness? Maybe my short is deeper in the harness, back near the box. I should fix this before jumping relays for fuel pump, right?

Are the CD wiring diagrams my best source of schematics? I hate asking for help like this. My 'fiche diagrams might as well be in greek. Have also found a trace coolant leak up high, probably crossover, so maybe I'll just pull the whole intake system and do a proper harness, sensor, injector revamp. Am starting to get frustrated here. Am pissed at whoever let this car get into this state of disrepair.

Looks like its time to return the car to the jackstands. Gonna be a long haul.

gf261

Chris, I'd like to see the pictures just in case. I had a similar problem with my 89'. I wound up with several burned wires on the rear of the CE panel. Be VERY careful as you continue to try to crank it over as there may be something grounded out. Have an extinguisher handy. My problem began while driving down the road and smoke began to come from beneath the passenger footwell. I shifted to neutral and cut it off immediately, but the damage was done. After tearing into it, it turned out that my upper radiator hose was resting against my ignition coil. The hose finally rubbed through the wire sheathing and pressed the bare wire against the metal rim of the coil. BINGO!!! Grounded out and melted the sheathing off the coil wire from the coil all the way to the CE panel. It actually got so hot that the outer wrap that held all the wires in the entire loom had a bright shiny line where it melted from the inside out. PM me or just post back here. I'm not expert by far, but I just got my buttoned back up this evening from the repair and may be able to offer a couple of shortcuts.

Landseer

Thanks for the reply.
Garrett, glad your car is operational, that failure had to have been very concerning when it happened.

Here are a few pics of wiring issues.

Does anyone here know what these particular damaged electricals control directly?
Do any of these directly control components associated with the injector / spark / start issue?

(There has been a headlight short according to PO.
It may be all this is the result of somebody putting a higher amp fuse in box to drive headlights.)

I realize I need the wiring diagrams to proceed, just looking for some starting places for now to get engine running.

CE unit


scorched wires


more damaged wires


burn through harness


melted insulation at ground near CE box


trauma around fuses


more fuses


shop dog. bored. was promised a ride. tired of waiting.

Landseer

Objective is get motor running, then sort thru all the other electrical stuff.

So far, here's my plan. Any input would be appreciated.

Track-down and fix injector(s) short.

Locate and measure brain voltages.

Jumper relays and attempt start.

New green wire, buy CD, check/buy new resistor pack for coil.
(my cheap meter defaults to 100ohm scale, and it maxed-out across each resistor)

Will keep battery disconnected and charged unless needed for troubleshooting.

Keep extinguisher handy.

Sounds like fun...

Mrmerlin

first thing to do is go to a good supply shop and buy a new set of good fuses,(.NOT HARBOR freight)........ before installing them run a fuse position check to make sure the fuse # is in the right slot try www.928GT.com for a fuse chart.

Next before connecting the battery I would pull the CE panel down and check to see where the fried wires are , you will find atleast 1 burned wire on the back.
Next i would open the back of the 14 pin connector at the hot post , and check for split insulation near where you found the thick black insulation split at the RT shock tower, then I would proceed to open the front wheel well covers and inspect the headlight harness where its clamped to the frame horns this is a known flex/weak link and a good place for wires to break

Landseer

OK, thanks. I will concentrate on circuit repair then.

gf261

Chris, EXACTLY what Mrmerlin said. 928gt.com has fuse and relay charts for specific model years. I felt nausea coming on when I looked at your pics. It's almost as if you took them of my car. My harness looked the same as yours, and also the sheathing was burned completely off the wire. You need to go ahead and pull the CE panel out, since I'd bet my next paycheck that you've got damage on the backside as well. Pardon if I'm preaching to the choir, but most of the harnesses that plug into the bottom portion have wiring that runs to the fuses up top at some point. My wire that burned through scorched a half dozen or so on the back side, which is probably where your multiple fuse trauma came from. When you unplug the big harnesses on the bottom, mark each one with the corresponding letter on the CE panel. Mine are A-W, except for the letter I, which isn't present. Mine are also marked individually from the factory, but a black Sharpie will make them much easier to identify when replacing. I'm not sure if 928gt has a chart for the harnesses at the bottom, but you can trace the wires from the culprit bare one to its mate on the back and then to the proper fuse. That might give you a place to start looking. I'll be away from my desktop the rest of the day, but tpr261@yahoo.com comes to my Blackberry, so drop me a note if you hit a snag and I'll try to provide some insight for you. Just put 928 in the subject so I'll know it's not spam.
ALSO!!!!!! Take LOTS of digital pics as you pull things loose. I assure you that they will be invaluable on reassembly.
Best of luck,
Garrett

Mrmerlin

just unbolt the CE panel before removing any connectors it will fall down and then you can see the back, it is probably a bad ground that has caused this but the headlight harness sounds like a causual factor

Jim bailey - 928 International

As I recall the coil power wire is bundled in the same front "headlight" harness .... !! if the wires outside are melted odds are so are the ones inside.