What could have I done?, Car is running on only 2 and 3. Options

[robkammer]

All: In prepping our BB for the vintage event next week I have done the following, along with a couple of fellow cult members. I had experienced a rather jolting banging at the right rear corner only in fifth gear. Between us, we diagnosed this as a transmission issue.
Pulled the tranny and took it to the good Doctor last week. He pulled it apart and found nothing major, only some minor wear items that he replaced.

Once back in the shop I looked more closely at the CV's.They were dry and binding badly. This was the problem. Ordered rebuilt's from George and installed them, when they FINALLY arrived.

All good, so we thought.

Got the axles in, wheels on, lowered the car and fired it up. Runs like , uh, crap.
Pulled the disty cap, Ok, new cap, rotor and points should do it. Nah.

Pulled plug wires 3#4, no change. It is running on 1#2 only.

Pulled #4 plug, beautiful. a nice shade of tan.

Put a timing light on all four plug wires, all are getting juice.

Called John at Air cooled Plus to see if there was any possibility that his flywheel work could be the cause. Nope.

He did grab a Bosch manual and alert us to a second set of contact points in the distributor, below the ignition points, that fire the injectors. Who knew?

Pulled the disty, cleaned the FI points, all good. Still running on 1&2.

Fellow cult member Jeff had a spare FI box and distributor, swapped boxes, no change. Pulled the FI points and tested continuity and they are performing just as the points in the car are, and also test the same.

Good continuity between the disty trigger contact and injector contacts on all four cylinders

Errlier, while I was waiting for parts, I did de-A/C the car. Pulled the condenser, receiver dryer, the underdash console and all of the hoses. Installed a correct tall console. I needed to pull some of the derelict wiring from the engine bay through the console to complete the process. I left the compressor in until I pull the engine this winter. It all went well without any drama.

At least I thought so

I can't think of anything in the passenger compartment that would affect the FI. We were only working in the back, pulling the transaxle and axle shafts. What could we possibly have touched to kill the two cylinders?

Any input would be welcome. At this point I'm relegated to taking another car to the event.

Cheers!
Rob

[JeffBowlsby]

Rob,

Have you verified that all three grounds are attached at the top rear engine case, tri-spade lugs? Cyls 1&2 and cyls 3&4 share paired injector grounds. Your cyl 3&4 ground lug connection may have fallen off, or be corroded. Causing those injectors to not fire.

PS your title says 2&3 only. That’s a different problem…if that’s the case your trigger points may be worn out or at least need regapping. Causing those injectors not to fire.

Be sure your FI harness is on top shape. Broken wires, corroded terminals etc can cause similar disfunctions.

[VaccaRabite]

Agree with Jeff that this sounds electrical and not mechanical.

Put a test light on your injector wires and see if they are firing. I bet they are NOT.
if they were, your spark plug would not have been tan. It would have been wet and black. or, as Jeff said, just look for the grounds you pulled out and forgot to replace.

Zach

[Superhawk996]

It sounds like you are open to some coaching on what you could have done.

Methodical troubleshooting with a DMM and/or test lamp probably would have gotten you to your event. Throwing parts at problems and remove & replace “testing” is rarely the most time effective solution. For whatever reason, this is a really popular thing for hobbyist’s to do so in no way is this a critique of you personally.

Easier said than done when you’re under pressure I know.

I was trained by USAF as an electronics tech and it was repeatedly drilled that methodical troubleshooting using the half-split method IS the fastest way to solve a problem - especially so when under pressure. We were often tested under the clock with problems that were intentionally designed to mislead. It was repeatedly proven to me that methodical half-split troubleshooting is the fastest approach.

Remove and replace testing often induces new problems and alters symptoms that will simply run you in circles.

Advice worth what you paid for it, or double your money back. (IMG:style_emoticons/default/beerchug.gif)

[DennisV]

methodical troubleshooting using the half-split method IS the fastest way to solve a problem

I think you have volunteered to write an article on the half-split method... (IMG:style_emoticons/default/smash.gif)

[Superhawk996]

methodical troubleshooting using the half-split method IS the fastest way to solve a problem

I think you have volunteered to write an article on the half-split method... (IMG:style_emoticons/default/smash.gif)

It’s very well documented. Google will get you there.



The example above implies we are troubleshooting an electrical signal but the concept is just as easily applied to mechanical devices like an engine.

Here is another explanation that is good and touches on how use of half-splitting works. Using half splitting you can determine the a particular card drawn from a deck of 52 cards with only six questions.
https://www.ecmweb.com/maintenance-repair-o...-half-splitting

[Dave_Darling]

Hah! That's like a binary search in computer science! (IMG:style_emoticons/default/smile.gif)

--DD

[Jack Standz]

Very good theory and practice. Thanks for suggesting it.

But, when you pull out the multimeter to see if you're getting voltage or continuity along that path/circuit, you turn it on and nothing.

Then you go get some "fresh" batteries for the meter, but, when you try to open the case it's a very small screw that you need to find a very small screwdriver, you go to dig it out from your old tool box, but then you remember you were using that particular screw driver to fix your glasses and it's at the office. You finally get the screw loose (maybe a grinder, if you can remember where you left it) and put the batteries in and, nothing. So, you need a multimeter to test if the "fresh" batteries are flat or is that old meter you've dropped maybe half a million times, is now broken?

After returning from the store with your new multimeter and a "few" extra tools, you've now completely forgotten what you needed to go to the store to get a multimeter for in the first place or even what a half-split methodology was or is.

You then repeatedly curse the DAPOs and buy an entire new wiring harness for your 50+ year old Porsche 914 'cause you're sick of half-splitting electrical problems on crusty virtually useless wiring that's been hacked up by half-ass*d, half-witted DAPOs, who don't know what a half-split troubleshooting process is. If I had half a mind, that's exactly what I'd do. YMMV.

Oh, and good luck with the fix. It does sound electrical.

[DRPHIL914]

Very good theory and practice. Thanks for suggesting it.

But, when you pull out the multimeter to see if you're getting voltage or continuity along that path/circuit, you turn it on and nothing.

Then you go get some "fresh" batteries for the meter, but, when you try to open the case it's a very small screw that you need to find a very small screwdriver, you go to dig it out from your old tool box, but then you remember you were using that particular screw driver to fix your glasses and it's at the office. You finally get the screw loose (maybe a grinder, if you can remember where you left it) and put the batteries in and, nothing. So, you need a multimeter to test if the "fresh" batteries are flat or is that old meter you've dropped maybe half a million times, is now broken?

After returning from the store with your new multimeter and a "few" extra tools, you've now completely forgotten what you needed to go to the store to get a multimeter for in the first place or even what a half-split methodology was or is.

You then repeatedly curse the DAPOs and buy an entire new wiring harness for your 50+ year old Porsche 914 'cause you're sick of half-splitting electrical problems on crusty virtually useless wiring that's been hacked up by half-ass*d, half-witted DAPOs, who don't know what a half-split troubleshooting process is. If I had half a mind, that's exactly what I'd do. YMMV.

Oh, and good luck with the fix. It does sound electrical.

(IMG:style_emoticons/default/agree.gif) AND

(IMG:style_emoticons/default/lol-2.gif)

[DRPHIL914]

Very good theory and practice. Thanks for suggesting it.

But, when you pull out the multimeter to see if you're getting voltage or continuity along that path/circuit, you turn it on and nothing.

Then you go get some "fresh" batteries for the meter, but, when you try to open the case it's a very small screw that you need to find a very small screwdriver, you go to dig it out from your old tool box, but then you remember you were using that particular screw driver to fix your glasses and it's at the office. You finally get the screw loose (maybe a grinder, if you can remember where you left it) and put the batteries in and, nothing. So, you need a multimeter to test if the "fresh" batteries are flat or is that old meter you've dropped maybe half a million times, is now broken?

After returning from the store with your new multimeter and a "few" extra tools, you've now completely forgotten what you needed to go to the store to get a multimeter for in the first place or even what a half-split methodology was or is.

You then repeatedly curse the DAPOs and buy an entire new wiring harness for your 50+ year old Porsche 914 'cause you're sick of half-splitting electrical problems on crusty virtually useless wiring that's been hacked up by half-ass*d, half-witted DAPOs, who don't know what a half-split troubleshooting process is. If I had half a mind, that's exactly what I'd do. YMMV.

Oh, and good luck with the fix. It does sound electrical.

(IMG:style_emoticons/default/agree.gif) AND

(IMG:style_emoticons/default/lol-2.gif)

oh forgot to add, agree with the FI points grounds- i had this very thing happen way back about 12 years ago, suddenly missing, and not sure exactly why then bad, only firing 2 , it was loose connection for one of the sets of FI grounds , - i now always start with checking grounds and connections! then go from there.

Hope it is that easy for you - i have forgotten to re attach the transmission ground strap too! we all have done stuff like this.

[Artfrombama]

Try a new ignition condenser.
Cheap and easy. A bad condenser will drive you crazy, will give a misfire not unlike you describe.

[Superhawk996]

Very good theory and practice. Thanks for suggesting it.

But, when you pull out the multimeter to see if you're getting voltage or continuity along that path/circuit, you turn it on and nothing.

Then you go get some "fresh" batteries for the meter, but, when you try to open the case it's a very small screw that you need to find a very small screwdriver, you go to dig it out from your old tool box, but then you remember you were using that particular screw driver to fix your glasses and it's at the office. You finally get the screw loose (maybe a grinder, if you can remember where you left it) and put the batteries in and, nothing. So, you need a multimeter to test if the "fresh" batteries are flat or is that old meter you've dropped maybe half a million times, is now broken?

After returning from the store with your new multimeter and a "few" extra tools, you've now completely forgotten what you needed to go to the store to get a multimeter for in the first place or even what a half-split methodology was or is.

You then repeatedly curse the DAPOs and buy an entire new wiring harness for your 50+ year old Porsche 914 'cause you're sick of half-splitting electrical problems on crusty virtually useless wiring that's been hacked up by half-ass*d, half-witted DAPOs, who don't know what a half-split troubleshooting process is. If I had half a mind, that's exactly what I'd do. YMMV.

Oh, and good luck with the fix. It does sound electrical.

Hmm. . . (IMG:style_emoticons/default/idea.gif) That all seems so familiar (IMG:style_emoticons/default/av-943.gif)

[robkammer]

Hey Fellas, it's all good. Found one of the engine ground wires had a broken connector. Didn't even consider these to be a problem as the harness was only two years old.
Heading out to the Put in Bay Vintage Sports Car races that start today and go through Thursday. We're not racers, but we'll be driving in the spectator class.
It's always a great event, and the featured marque the year is Porsche!
Cheers

https://www.visitputinbay.org/event/put-in-bay-road-race/

[VaccaRabite]

It happens!
I had a wire yanked off this summer about 200 miles from home that had to be fixed at a gas station at night under the 914. Best I can figure, a stone in a parking lot grabbed it when we had dinner a few hours earlier. Soon as it was fixed the car was awesome again.

Zach

[Jack Standz]

Hey Fellas, it's all good. Found one of the engine ground wires had a broken connector. Didn't even consider these to be a problem as the harness was only two years old.
Heading out to the Put in Bay Vintage Sports Car races that start today and go through Thursday. We're not racers, but we'll be driving in the spectator class.
It's always a great event, and the featured marque the year is Porsche!
Cheers

https://www.visitputinbay.org/event/put-in-bay-road-race/

Good job!

And I see you already got the new wiring harness, so you were at least halfway there (IMG:style_emoticons/default/smile.gif).