carrera 3.2 running on 4 cylinders after re-install

[andyt11]

Had the engine out for valve guides and a few other things over the winter. I removed the engine myself and shipped it off to someone more competent than myself for the actual rebuild. I've now finished assembling and putting it back in the car.

Started it last night for the first time and its obviously only on 5 cylinders. So I turned it off pretty soon. (its not all bad mind, no bad noises and no smoke)

Then I tried to figure which cylinder is off by pulling the injector plugs off one at a time and listening for a change. I did 1 2 and then 3 and all affected the running of the engine. Then I got to 4 and bingo, no change.

So I pulled the plug on 4 and its still brand new. Never fired in its life. So I swapped it with the plug in 1. The problem stayed at cylinder 4.

So then I tested the HT lead, just under 3k ohms per bentley. I tested the injector across its terminals and got 2.4 ohms, should be between 2 and 3 ohms according to bentley so that's ok too.

Then I swapped HT leads 4 and 5 (at both ends) to see if the problem could be the lead. No different. 4 is still not firing. However, what I never noticed all day is that neither is 5. This car has been running on 4 cylinders all day. It doesn't matter what I do, 4 and 5 are not firing.

I have triple checked the plug leads are in the correct order. At this point there must be a reason 4 and 5 are not getting a spark or not getting fuel. Or not being told by the computer to squirt fuel.

I've also swapped out the DME relay for a spare with no change.

Now I'm done for the night and heading to the bar. If any of you can think of a reason why 4 and 5 would be affected like this, please let me know. We are moving house, I'd prefer it if the porsche didn't arrive at the new house on a flat bed!! My wife would prefer it if I'd spend some time packing the furniture up!

Also, please don't assume I know much, this is by far the biggest project I under took ever.

Car is an 88 coupe, new dizzy cap and rotor, new plain jane NGK plugs. Car is 100% stock.

Thanks in advance all.

Regards

andy

[yelcab1]

Do a compression check on 4 and 5.

[andyt11]

I don't have the equipment to do a compression test.

I could invest in it, but what makes you think 1, 2, 3 and 6 would be sound while 4 and 5 are not? (not trying to be argumentative - just asking)

[hcoles]

could be one side is not firing - this happened to me - I had one cam 180 out
this can be checked by looking at how the valves are going up and down while turning the crank compared to the rotor position, have to take the top valve cover off the offending side

[andyt11]

I checked number six. It is working as it should. Would 6 fire if the cam was 180 out?

[john walker's workshop]

swap an injector from a running cylinder. check valve clearance.

[hcoles]

no, if the header on #6 is hot and others on that side are cold the cam out is not the issue

[andyt11]

Solved it. A local PCA guy came over and we did a bit more work.

First we confirmed the injectors were getting power following the bentley manual. Then once we confirmed that was good, we swapped the two dodgey injectors to different cylinders. We cleaned them at the same time, thinking that we would either prove I need to buy two new injectors, or fix the problem.

Turned out they must have just been dirty. A quick blast with carb cleaner and we are on six again.

Thanks for the input all.

So, now that I have my car back again, its lashing down with rain and we are getting 4 inches of snow tomorrow?! It's may now isnt it?

[dienstuhr]

Well done Andy! On track for the PCA meeting on Weds.!

[efhughes3]

Even clean injectors can stick if they sit a while.