Throttle issues and now car won't start

[Captain Obvious]

Zed Head, You're absolutely right. It's not the thermotime. I missed the mark on that and thanks for covering for me.

 

And on your FI relay, that's an exact problem I've seen with other crispy coils. They work fine when cold, but when you put power on them for long enough, they naturally heat up a little because of the coil resistance and cause their own internal failure to open up. Until they cool down again of course... Tough to find sometimes because of the intermittency.

 

 

 

[Zed Head]

Nice find.  Yes, that is the switch I was talking about and it should only affect ignition timing by about 6 degrees.  When it's disconnected, like yours, timing just stays where it would be when warm anyway.  Many people don't use that feature anymore, it's only there for cold engine emissions.  It never even gets tested.

 

Notice the two sensors with the two prong, injector style, connectors.  The big one on the left is the thermotime switch, and the other, with the white connector, is the coolant sensor.  But without knowing which wire is which, you can't really tell if they've been switched by accident, without going to the ECU connector.  Hard to tell if you're flooded or lean, but knowing that the coolant sensor is right is very important.  It's the most important sensor on the engine, besides the AFM.  I would at least take that one measurement at the ECU connector.

 

If you have some starting fluid you might see if it will start that way.  If it starts, runs for a few seconds, then dies, that's a clue.

 

Also, try to add lots of detail to the problem description.  "Tries to start" could mean it runs for ten seconds then dies, or pops just once.  Totally different causes for those two things.

 

CO - I finally realized why that extra EFI/Pump relay was in the car.  I had thought it was a typical mis-diagnosis by a PO.  Not the case.  There were signs of heat in the cover, brown spatter marks from vaporized insulation, I assume.  I got a lot of miles out of it though before it crapped out again.

Edited April 28, 2015 by Zed Head

[Blinkerfluid22]

Sorry i havent replied in a while, i have been traveling. I was able to take measurements at the ECU connector and everything seemed ok, so i went and did a compression test. Here are the results: 

1- *DEAD* 0
2- 195
3- 180
4- 210
5- 205
6- 210

 

So where do i go from here? Obviously something happened to cylinder 1, but what about the readings in 2-3? Could the zero compression be valve related or something worse?

[EuroDat]

0 compression doesn't sound good. Could be a stuck valve, hole in the piston, burnt valve or something wrong with the rockers not opening the vavles.

 

You can narrow it down with a leak down test. That is what I would do before opening it up.

A quick description on how to do it.

Turn the engine to TDC number one cylinder. Check it on the compression stroke by checking the rotor button in the distributor is pointing to number 1 sparkplug lead.

Put the car in 4th gear and handbrake on to stop the engine turning.

You will need a compressor and a fitting for the sparkplug hole. My compression tester has an adapter that does the job perfectly. See photo, Its retro but I like it. The engine can spin a little, maybe not in this case, because the air pushes the piston down until the slack in the drivetrain is gone.

Apply air via the sparkplug hole and listen to the exhaust, Oil filler cap and carburetor. It should be cushing out one of those. Hopefully its not the oil filler cap. That most certainly means piston failure. If its valves, I would then take the cover off and investigate further.

 

Chas.

[Blinkerfluid22]

Well i finally got to the bottom of it. The oil spray bar for the cam clogged causing everything to overheat. This eventually cause a valve to drop in cylinder 1 and ruined the cam. Looks like i have a fun an expensive road ahead with a new cam, head rebuild and new rockers. 

[siteunseen]

Well i finally got to the bottom of it. The oil spray bar for the cam clogged causing everything to overheat. This eventually cause a valve to drop in cylinder 1 and ruined the cam. Looks like i have a fun an expensive road ahead with a new cam, head rebuild and new rockers. 

Ouch!

 

Yeah, very fun road.  I'm on it now with my E31.  Maybe you can find a deal on a cylinder head that's ready to bolt on.  I found a fresh N42 at a machine shop.  They had reworked it for a guy and he never came back so I got it for their cost, $250.  I had to ask the folks on here if that was an okay deal, I had an N47 originally.  Some of the replies were funny, "terrible head, boat anchor, better to melt down the aluminium and scrap it, BUT I'll take it off your hands and save you the headache". 

[EuroDat]

Thats bad luck. Hope the vavle hasn't done irreparable damage to the piston. They stick in the open position and then piston contact when it comes back up the bore.