73 2.0 Has Issues, Ran GREAT and then it didn't Options

[Minerva's 914]

1973 914 2.0 restored and motor rebuilt by Fat Performance and installed by Black Forest Racing. We've driven her off and on for about 750 over the past year with no problems, in fact she ran fantastic .... until she didn't. Driving around the neighborhood last week the engine bucked a few times with the tach dropping to zero before bouncing back to normal, downshifted and it seemed better only to return again while cruising along at 2800 RPM, down shifted again and since we were only a block away from home made it with no drama. Was thinking maybe an electrical issue shorting out the ignition.

I started the car yesterday evening and backed out of the garage and it stopped dead in her tracks. Turned the key to 0 then back on again and no fuel pump buzz. Proceeded to engage the starter and after several seconds of cranking I returned the switch off, then back on again. No fuel pump buzz.

Checked the relay in the circuit board, switching out the relays, no change. Checked the fuses and connections seem clean so I jumped directly from the battery to pin 12 on the circuit board, turn the key to 1 and got the fuel pump buzz, turned off and back on again got the fuel pump to work.

What do you guys think should be my next step? I planning to get on it early tomorrow and start chasing the wiring but hope someone here might help me narrow down the possibilities. Plan to remove the circuit board, turn it over and check the connections and double check the grounds and then check continuity from the brain, then work my way to the inside fuse panel and wherever else the electrons are circulated before reaching the fuel pump.

As always THANK you guys for all you do to help the 914 live on!!!

Brady

[iamchappy]

The temp sensor mounted in the head goiing bad can do that.. If your car runs when jumping the relay to excite the fuel pump i would guess the temp sensor.

[Minerva's 914]

The temp sensor mounted in the head goiing bad can do that.. If your car runs when jumping the relay to excite the fuel pump i would guess the temp sensor.

Hmmm, didn't think of that but makes sense. I'll test that and provide feedback.

Thx!!!

[Minerva's 914]

The temp sensor mounted in the head goiing bad can do that.. If your car runs when jumping the relay to excite the fuel pump i would guess the temp sensor.

Hmmm, didn't think of that but makes sense. I'll test that and provide feedback.

Thx!!!

Hmm, checked the resistance value while still installed in the head reading is 2.4 which I believe enrich the cold start-up but not effect the start up sequence. Black Forest Racing installed a new HTS when they were installing and setting up the FI, though it still has the original inline resister as updated by Porsche.

Also a little confused as to how / why the HTS would interrupt power to the fuel pump, my problem is no power is getting to the pump thru the normal start-up procedure and power pathways, if I bypass the normal route by jumping power to pin 12 the fuel pump 1 second buzzes normally at ignition key to position 1.

Maybe I'm missing something (IMG:style_emoticons/default/confused24.gif)

Still search for 914 perfection.

[JeffBowlsby]

Maybe you tried two bad relays? Or the circuit board is toast?

[Minerva's 914]

Maybe you tried two bad relays? Or the circuit board is toast?

Yeah I thought of the two replay wild goose chase, jumped pole 86 + and 85 - and the replay clicks so I know it's good. I also just now jumped 12v directly to the relay and relay board by attaching an alligator clip to pole #86 on the relay then carefully inserted it back on the relay board, added a 20a fuse inline then connected to the battery positive cable. The fuel pump started running straight away.

The electron chase continues

[Minerva's 914]

Maybe you tried two bad relays? Or the circuit board is toast?

Yeah I thought of the two replay wild goose chase, jumped pole 86 + and 85 - and the replay clicks so I know it's good. I also just now jumped 12v directly to the relay and relay board by attaching an alligator clip to pole #86 on the relay then carefully inserted it back on the relay board, added a 20a fuse inline then connected to the battery positive cable. The fuel pump started running straight away.

The electron chase continues

RELAY! RELAY! Sheesh, autocorrect doesn't seem to learn how often I cuss and how little I talk about ducks.

[Rob-O]

Ignition switch.

[IronHillRestorations]

Trigger points?

[Minerva's 914]

Okay, here's were we are;

Pulled the circuit board checked the bottom which was in pretty good shape. No signs of breech or corrosion. Chipped off a tiny bit under the fuel pump relay and no further evidence of problems so I resealed with epoxy. Next pulled the ECU and ran the resistance or voltage as required to test back thru the wiring all checked out perfect. I then reconnected the ECU, reattached the battery ground, turned the key and WOW, I got that heart warming fuel pump buzz at switch on. Turn over the engine and after several revolutions it fired up! Ran for 10 seconds or so and died. Turn the key to OFF then back ON, again got the buzz but this time it would not fire. Back under the hood to double check that nothing was amiss with the ignition, checked for any vacuum hose loose then tried it again. Same results, fuel pump buzz at ON, but would not fire. Pulled the ECU harness and reassembled, then back to where we were in the beginning, no fuel pump buzz at switch ON.

Looks to me as if I've got a bad ECU, anyone agree or disagree?

Next question, where can I source a replacement?

(IMG:style_emoticons/default/headbang.gif)

[JeffBowlsby]

The ECU would be the last thing to suspect, they are very reliable. I have seen a bad one but very infrequently. I have the equipment to check its functions, but check other things first.

How does your harness look? New, old? Terminals nice and clean or corroded?

Still suspect your relay board given its connection to the fuel pump circuitry. Did you run a full continuity check on all its circuits?

[Minerva's 914]

The ECU would be the last thing to suspect, they are very reliable. I have seen a bad one but very infrequently. I have the equipment to check its functions, but check other things first.

How does your harness look? New, old? Terminals nice and clean or corroded?

Still suspect your relay board given its connection to the fuel pump circuitry. Did you run a full continuity check on all its circuits?

Harness looks good, no signs of corrosion, breakage nor browning from heat. I only visually checked the circuit board but did jump 12v to 86 pin on the relay while plugged in as described above and ran 12v jumper to pin 12 on the circuit board both of which buzzed the pump. Checked resistance between contact 19 on the ECU harness and relay plate terminal III, the ECU control line for the fuel pump, read 0.24 ohms.Checked voltage on 16 and 24 ECU harness got 12.54 volts on both. So as I'm writing this I realize that your thinking makes sense about looking closer at the circuit board, although it is strange that unplugging and plugging back the ECU harness would make and break the connection to the pump operation and would the curium board effect the running of the ignition since when the pump was running the car would not run.

Thanks for your help

[Dave_Darling]

If the tach drops to 0 even though the engine is still spinning over (even though it isn't firing) then your ignition system has a problem. Could be the power to it, could be the switching part, but something in there has a problem.

If your "tach goes to 0" didn't mean what I said, above, then it's much less of a clue.

Still, not a bad idea to verify that your'e getting spark when the engine won't run.

--DD

[Minerva's 914]

If the tach drops to 0 even though the engine is still spinning over (even though it isn't firing) then your ignition system has a problem. Could be the power to it, could be the switching part, but something in there has a problem.

If your "tach goes to 0" didn't mean what I said, above, then it's much less of a clue.

Still, not a bad idea to verify that your'e getting spark when the engine won't run.

--DD

Yes, the tach dropped to zero and I agree that can only mean a short / grounding in the ignition system. That was the first intermittent and momentary failure as I was rolling with the clutch engaged it fired back up and continued and at that time the fuel pump was not an issue. The fuel pump problem began the next attempt to drive the car. I started the car normally, backed out of the garage and the car died. No missing and then it died, it just stopped running. I can't confirm at that time that the tach went to zero as I was looking back over my shoulder when it happened but it felt the same as the earilier failures. The difference was this time I was not rolling fast enough to re-fire and when I tried to restart the fuel pump was silent at ignition key ON. So if both problems are related then I am looking for a single source that controls both the fuel pump and ignition. Unless two separate systems failed at roughly the same time, not impossible I guess.

Thank you guys for listening and contributing to the care and feeding of these cars that after 45 years we still love and nurture. I almost feel like I'm the 914 version of an AA member, "Hi my name is Brady Lambert. I am a 914 owner" but you know what, even at this time when I'm struggling to heal my little Alaska Blue baby back to health I still love her. Yes, even with the $30,000+ that I put into the restoration, I don't regret a single penny or time spent on it. The fact that this was my wife's first new car purchased with her own money back in May 1973 makes this a forever car. Okay, my 987.2 Boxster is faster, handles as well or better, has A/C and the top goes down with the push of a button, the seats are heated and cooled and as good as it looks, it never gets the reaction that the 914 does. I had a guy chase me to the mail kiosk in order to tell me that he always wanted a 914 back in the day but could never get his hands on one. That makes me proud that we are keeping these cars on the road doing what they were intended to do, be driven. Here's a photo and link to the video of Minerva and her car on the day of her 16th birthday (she's a leap year baby and only has a birthday every 4 years, so you do the math) when I gave the 914 back to her after 7 years restoration and had not driven it since 1992.

BTW, the seats that were in the car are not correct, the proper tan seats were not finished at that time so I stuck a set of brown ones in for the birthday thing, the proper tan seat are now finished and the brown ones are for sale if anyone needs a pair, that are in perfect shape.

Oh, and one more thing, in the video you'll notice Minerva start to pull away then stop and look at me and you'll hear me say "Over to the left and back" as I made the movement with my hand showing her the way to first. The gear shift knob was also not on the car and she forgot about the first gear position, LOL

https://www.flickr.com/photos/bradylambert/...eposted-public/

[ottox914]

Had a similar problem with my car.

Ignition switch. There is a small plastic piece that is sort of an interface between the mechanical turn of the key cylinder and the electrical contacts that sent power here and there when the key is turned position 1 or 2 Give away for me was no fuel pump buzz and no spark when turning over. I checked fuses and relays finding nothing wrong. Was thinking ecu issue as well, but couldn't believe that was it. Pull a plug wire and put an extra plug in it, have someone spin the motor over. The part is not all that $$ and can be swapped out in 30 min or less.

NOTE- my car us running SDS ecu, not stock, and the ecu controls both fuel and spark. So no fuel or spark had me thinking of what would prevent ecu from doing, well, anything. Its been awhile since I messed with a stock system, but I expect the same clues might lead to the same solution.

[mepstein]

Due to aftermarket shift knobs, many people miss 1st when they get their 914.

[Minerva's 914]

Had a similar problem with my car.

Ignition switch. There is a small plastic piece that is sort of an interface between the mechanical turn of the key cylinder and the electrical contacts that sent power here and there when the key is turned position 1 or 2 Give away for me was no fuel pump buzz and no spark when turning over. I checked fuses and relays finding nothing wrong. Was thinking ecu issue as well, but couldn't believe that was it. Pull a plug wire and put an extra plug in it, have someone spin the motor over. The part is not all that $$ and can be swapped out in 30 min or less.

NOTE- my car us running SDS ecu, not stock, and the ecu controls both fuel and spark. So no fuel or spark had me thinking of what would prevent ecu from doing, well, anything. Its been awhile since I messed with a stock system, but I expect the same clues might lead to the same solution.

Excellent advice and makes sense! Thanks, I'll get on that and report back. Rob-O had suggested the ignition switch earlier but I got sidetracked chasing the ECU theory so thanks to R-O as well.

[Minerva's 914]

Due to aftermarket shift knobs, many people miss 1st when they get their 914.

... but you'd not expect that from someone who drove the car for so long. Okay, so it has 80,000 original miles and I'm sure I put 70% of those miles on it, still I had to laugh.

[JamesM]

If the tach drops to 0 even though the engine is still spinning over (even though it isn't firing) then your ignition system has a problem. Could be the power to it, could be the switching part, but something in there has a problem.

If your "tach goes to 0" didn't mean what I said, above, then it's much less of a clue.

Still, not a bad idea to verify that your'e getting spark when the engine won't run.

--DD

This is exactly what I was thinking, if the tach pegged to 0 when the engine lost power the problem isnt going to be with your fuel delivery. Signal wire for the tach attaches directly to your coil. Start at the ignition system and work back from there. Are you getting spark?

[Minerva's 914]

Okay, so after a long delay involving travel, photography projects, holidays, flu and snow / cold weather. I finally got back on this project. If you'd care to know the whole background of this mystery jump back to the beginning and follow the various symptoms, suggestions, and fixes tried.

I had proofed the fuel pump by running a jump straight from the battery to fuel pump relay pin 85 on the circuit board, the fuel pump ran continuously, which to me proved to me a) the fuel pump was functioning properly and b) the circuit from pin 85 to the pump was good. I switched out a borrowed ECU and no change as the problem remained. I checked all of the power wiring and power circuit board continuity and all were fine. I removed the steering wheel and found the starter switch had a brown spot indicating it had gotten hot at some point so I replaced it with a new one thinking for sure that was the problem. No change but at least I know have avoided a future problem.

That's where I stopped back in September.

After thinking about it over the winter months I realized I was only thinking about power supply. So I started to check ground. Checking the obvious ground connections with the wiring I then moved to the circuit board. I checked the 14 pin connector to the relay board, pin 10 (ground) to the fuel pump power replay pin 86 by checking the continuity of pin 86 to ground. It failed, no continuity.meaning a bad circuit board!

I located a source for rebuilt circuit board "High Performance House" in Redwood City, CA, installed it yesterday and........

IT'S ALIVE!!!

www.highperformancehouse.com



Thanks to everyone who offered up suggestions. This is a great resource, you guys rock.