914 Misfire Problem Help

PJ UK · 02-18-2003, 10:26 AM

Heelp!!

I have a 1976 914/4 2.0 originally from California and exported to the UK about 10yrs ago. All of the smog eqpt was removed by a garage when I bought it. It ran fine until about 5 years ago and it has been stored since. Trying to get it running again has been driving me mad.

It starts without any problem hot or cold and idles @ ~1500rpm The problem is that it is not firing at all on Cyl #3 throughout rpm range (when dist->plug lead removed no change in engine note). When revved the exhaust pops and I get plumes of white smoke. I have removed the spark plug and it is wet with petrol, when plug connected to the lead and held against earth it appears to be sparking OK. The other plugs are a bit sooty but not massively. The distributor appears to be a electronic ignition reather than CB points/condenser etc and I assume this is working OK as the other cylinders are fine.

So far I have changed dist cap, rotor, leads, plugs, vacuum hoses, swappped the injector with Cyl #4 (miss stays on #3), set up the timing, checked/adjusted valve clearances. Cylinder compression is approx 95lbs which is a little lower than the others which are around 115 - 120 lbs.

Is this compression difference enough for it not to fire at all and is there anything else that I can try as I am really scratching my head now.....

Thanks for your help

PJ

tryan · 11:09 AM

try some good old points and change the plugs again. yellow or blue sparky ?

is the fuel 5 years old? if so get rid of it.

trigger points okay?

Walker914 · 02-18-2003, 11:13 AM

My engine had a loose valve seat that wallowed out the head, but luckily never dropped. My engine ran ok, but never seemed to make much power. One of the cylinders always had a wet plug, but seemed to be getting spark. I couldn't figure it out till, I did the compression check. Three were good, the one with the wet plug had low compression or no compression(can't remember exactly). Your engine may be starting to have the same problem. I would seriously consider dropping the engine in your car and taking a look before you do major engine damage.
It sounds your car has been sitting for a few years. If an engine sits for a while, a valve can stick to its seat and when it's turned over for the first time pull the seat out of the head.

Walker914 · 02-18-2003, 11:18 AM

Oh, when I say OK, my engine didn't idle after it got hot. It started fine and ran OK at higher revs, but once hot it wanted to stall at idle.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

95 PSI is not low enough compression to not fire. It also indicates that the valves are sealing OK (but probably not great). It is low, though.

Check the condition of the cam that operates the points. Or better yet, discard the points for an electronic replacement. Pertronix has had some quality problems, Crane XR700 or Compufire (don't know the part number) seem to not have those issues. I know you said you had a good spark, but...

How does the timing and dwell look?

Does the #3 plug squirt fuel at all? Disconnecting the ignition and stiking the injectors into glass jars can help you see that. Crank the starter for X amount of time and take a look at the injectors and spray pattern. After that amount of time, take a look at how much fuel has come out.

You need three things for the engine to run--1) air (or compression), 2) Fuel, 3) spark. After that, you come to when the spark happens, and how much fuel you get.

--DD

John Rogers · 02-18-2003, 07:26 PM

Snap-On makes a nifty tool that measures the voltage AT the spark plug so you can see if the power is getting there. Try to see if you can find a shop or someone that can measure the voltage at the plug. The wire could be shorting to the sheet metal, have a open in the wire, bad connector at either end. Try starting the engine at night, with no lights in the engine compt at look for the arching of the plug voltage. Good luck.

PJ UK · 02-19-2003, 09:06 AM

Thanks for the replies -

I have tried the trigger points already, I should have mentioned that. I have removed the injectors from #3 and #4 and they are firing about the same amount of fuel. I will get the dwell angle checked as I had the distributor out for the trigger points. I will also get the voltage at the plug checked. If it is none of those then I will pull the engine and give the cylinder head a good eyeballing!

Thanks again to everyone for the advice - Great forum!! :-)

PJ

tryan · 02-19-2003, 10:10 AM

do check the plug wires before you start pulling heads. follow johns advise about looking at night. spraying the wires with a water bottle works for intermitent misfirings. you could have a burnt sparkplug connector also. a blue spark is what you want.

norustscott · norustscott's Garage

My vote is with teh vavle. At the very least adjust them first.