'74 2L Starts Then Dies, Never a convenient time... Options

[GregAmy]

Nice beautiful New England Day, heading off to the Manchester CT car show and...car won't start. Cranks, a few cylinders fire, then it dies. I cycle the key and hear the pump running and then stop (as before) and same thing: spits then dies.

I tried cycling the key a few times, with the mindset of building more pressure, and it spits a few more cylinders then dies. Even got it to rev a little bit with a half-dozen key cycles, but always dies.

Only other symptoms is that I noticed the last time I drove it earlier in the week it was dying when I put in the clutch. Was not consistent, only did ti a few times, but that was unusual behavior.

Stock 2L fuel injection, but with cold start and idle air bypass systems disabled; been running fine like this for the several years I've had it.

Checked all the relays, each works with the heater blower. Swapping them makes no difference (which I expected, given the pump cycles with the key). My guess is that however the pump is supposed to continue to run after releasing the key, it's not getting the power it needs (just a guess, I've not gotten under there with a voltmeter to verify). The wiring diagrams are not clear (to me) how that power is applied to the fuel pump relay.

Any way to quickly salvage my afternoon trip to the car show, or am I using my beautiful afternoon to swap the street car onto the lift for extended diagnosis?

40-yr-old electrics, gotta love 'em.

- GA

[GregAmy]

So I removed the relay panel harness connector, the one that I think goes to the computer, cleaned it and put some dielectric grease on it...and it starts.

But do I trust it? Well, I do have AAA...

Can anyone explain the control functions of the fuel pump on the D-Jet?

GA, here we go...

[TheCabinetmaker]

Its all in the Brad Anders website. Brads 914 2.0L page.

[GregAmy]

Made it to the show and back, but it was cutting out on me on the highway, so there's clearly an outstanding issue. When I got home I wiggled and tapped everything - relays, plate, fuses, wiring harness - and it didn't die.

Electrical problems, yay.

I'm guessing you mean this? Thanks for the reference. However, I'm not getting any info from that page except for the intro.

http://members.rennlist.com/pbanders/FPChecklist_frame.htm

[TheCabinetmaker]

Go here

http://members.rennlist.com/pbanders/DJetParts.htm

[boxsterfan]

Stock pump in stock location on stock wiring?

If I recall, turning the key on will allow the pump to run for a few seconds before it turns off. Of course, if you are cranking the car to start the pump is to keep running.

Definitely sounds like electrical issue. Perhaps check all of your chassis ground wires. 40+ year old wires are not fun to troubleshoot. That pbanders site is the best D-Jet reference on the planet.

Other oddball stuff to look at (just throwing these out there):

1. Distributor/coil setup- You getting spark consistently?
2. Cracked relay board (you'll have to remove it and have a good look).
3. Voltage regulator issue?

Best of luck.

[GregAmy]

Thanks. Do you know if "19 and relay plate terminal III (white plug, back left corner) - ECU control line for the fuel pump relay" is hot all the time that the car is running?

Edit: disregard. Anders links to a discussion of the ECU and cofirms that as long as the engine is above 100RPM the pump relay control circuit is powered.

http://members.rennlist.com/pbanders/ecu.htm

[GregAmy]

Ok, so maybe this thing isn't worked out yet...

Fuel pump is priming with ignition on, so at least that's resolved. However yesterday I took it for a nice long drive, started/ran fine, no hiccups. However 3 hours later when I went to leave, it started fine (fuel pump primed) but then it kept dying. Thinking it was the lack or AAR and cold start valve, I could kinda keep it running with some throttle, but it was not running smoothly; it would have a random hard miss, and would try to die.

I was following someone to the next stop and it was driving terribly: I mean HARD shutoffs and restarts, not like a dead cylinder miss but like a shut off engine miss. It would die when I came to a stop but would kinda restart, and I could keep it running with some throttle but still not smoothly. As I'm cruising down the road it was HARD shutting off then coming back on, and feeling overall unhappy (like a flooded spark plug) slightly less so with full throttle but it never went away. I thought at one point I was going to have to pull over but kept going, and then...

...all of a sudden it smoothed out. No problems for the rest of the 30-minute trip. Car ran fine and smooth and never stalled again.

Starting up 2 hours later cold, same problem: starting and die, could keep running with throttle but very un-smooth, like a flooded cylinder. I let it warm up for a few minutes and it got better but when I hit the road I got those hard stalls and restarts, and then...

...it warmed up and it was fine for the rest of the trip.

I had these same symptoms that last time I drove the car a few weeks ago, before I replaced the relay plate. I thought it was related to the bad relay plate, that maybe the fuel pump was shutting off. I've replaced the plate and the relay, and it's still there.

I'm stumped, even more so because it seems to be related to the temperature of the engine. Dead cold the problem is not there, partially hot it's there with a vengeance, completely warmed up it's gone.

I've checked the head temp sensor and it's within book range, cold and hot.

Ideas appreciated.

Greg

[Sleepin]

Fuel pump? Sometimes when fuel pumps start to fail, they will intermittently operate. This happened to me on the way to RRC a couple years back. I called SLITS (I'm going to miss being able to do that) and he suggested direct wiring the pump to the battery as an emergency fix, then gave me the NAPA part number for the replacement pump. Sure enough, it worked fine for a while (hour or two) being directly wired up. Once I replaced the pump, all was fine once again.

*note...you get funny looks driving down the road with jumper cables running from the battery to the front trunk (1975 model).

[BeatNavy]

I've checked the head temp sensor and it's within book range, cold and hot.

Sensor itself may be fine but what's the condition of your wiring harness? I'd look for kinks/breaks that can create open circuit intermittently from CHT to ECU. Inspect the actual connection closely. I have experienced bad CHT symptoms when it was the wiring harness not the sensor itself. One reason I bought one of Jeff's new wiring harnesses...

Like others have said - it sounds electrical - like a connection is sketchy somewhere (CHT, MPS, T1 Sensor, etc.) that's making it either run too rich or completely cutting off (e.g., fuel pump) when it acts up.

[76-914]

I'm going to suggest that you install a FP pressure gage. If your CW and don't want to add one to the interior portion you can install a mech FP sender/gage in the engine compartment. It greatly improves diagnostics when you can rule out a major (fuel) player. Also, try jiggling your ignition key next time it happens to see if there is a change. (IMG:style_emoticons/default/beerchug.gif)

[GregAmy]

Thanks for the tips.

I don't think it's the fuel pump itself. I replaced mine a couple years ago with a 2-port NAPA pump/kit I got from Chris (Tangerine) so it's probably OK. Plus, it's correlated to temperature of the engine and there's not a lot of temp change up there (it's mounted under the tank).

Wiring I can certainly understand. One easy trick I can do is run some wire from the power terminal on the pump to an LED in the cockpit and see if I get a flickering light correlating to this problem. If I do get a flickering then I can move the wires back to the replay board, both output and relay control, and try to nail down where the prob may be.

As for the head temp sensor...man, trying to troubleshoot a random problem there will be damned near impossible. Is it correct that the fuel injection shuts off if it doesn't have a good temp reading? If not, what are symptoms of a bad sensor/circuit there? Jeez I hate 40-yr-old wiring. But can't float the cost of a new harness right now.

I have four race weekends in a row coming up*, so this is going to be an October project. Thanks for the advice.

- GA

* LRP Historics (driver observer), SCCA Regional at Palmer (914 race car comes out for the first time), and Mid Ohio SCCA Runoffs (competing). If you're in the area at any of these stop by and say hello, #33 STL Honda Civic Si or orange 914

[DRPHIL914]

Thanks for the tips.

I don't think it's the fuel pump itself. I replaced mine a couple years ago with a 2-port NAPA pump/kit I got from Chris (Tangerine) so it's probably OK. Plus, it's correlated to temperature of the engine and there's not a lot of temp change up there (it's mounted under the tank).

Wiring I can certainly understand. One easy trick I can do is run some wire from the power terminal on the pump to an LED in the cockpit and see if I get a flickering light correlating to this problem. If I do get a flickering then I can move the wires back to the replay board, both output and relay control, and try to nail down where the prob may be.

As for the head temp sensor...man, trying to troubleshoot a random problem there will be damned near impossible. Is it correct that the fuel injection shuts off if it doesn't have a good temp reading? If not, what are symptoms of a bad sensor/circuit there? Jeez I hate 40-yr-old wiring. But can't float the cost of a new harness right now.

I have four race weekends in a row coming up*, so this is going to be an October project. Thanks for the advice.

- GA

* LRP Historics (driver observer), SCCA Regional at Palmer (914 race car comes out for the first time), and Mid Ohio SCCA Runoffs (competing). If you're in the area at any of these stop by and say hello, #33 STL Honda Civic Si or orange 914

I might suggest the MPS failing - I had this exact scenario last winter and it ended up being the MPS, - and it held vacuum, its diaphragm was not torn- it was failing electroically - I have a A/F meter- it was failing LEAN not rich like the usual default, so it would do the same thing you are seeing- but yes a CHT circuit shorting out will do this and if the #3 plug wire is close to the CHT wire it can cause interference as well. , - but if I had to guess ? 1. MPS, 2. CHT 3. your grounds for the FI at the back of the case- I had this happen this spring they were vibrating off - and all of a sudden running on 2 cylinders- so check those- I soldered mine on so they would quit coming off and I have a fairly new harness from Jeff B- also #4. check the tightness of the injector connectors they loosen with time - had this happen to me on my way back from Manchester 2 weeks ago after picking the car up from Chris. - Jeff Bowlsby posted a picture on my thread about how to tighten these.

- some times the only way is to do the process of elimination - but one thing at a time- try a spare CHT, or MPS first. - and I now have a Pressure gauge in line so I know if the fuel pressure is exactly where it has to be.- my pump recently went out or was on its way out- 5 years old napa pump, but it was still running but making a ton of noise and so I replaced it cause I had a spare Bosch in the shop- like night and day - Good luck, looking forward to hearing which issue it is! oh the fun of 40 year old cars and parts!!!!

Phil

[Shadowfax]

What type of plugs are you using and what is their condition? I suspect one or more could possibly be fouled.

[BeatNavy]

As for the head temp sensor...man, trying to troubleshoot a random problem there will be damned near impossible. Is it correct that the fuel injection shuts off if it doesn't have a good temp reading? If not, what are symptoms of a bad sensor/circuit there?

No, a bad circuit there is interpreted by the ECU as a cold engine, and it lengthens the pulse for the injectors thinking it's a cold condition. On a warming or warmed up engine it effectively floods the engine and kills it. That's my understanding anyway.

I agree with Phil. Take each component you can think of and test it individually as well as its actual circuit to the ECU. The more suspects you can rule out, the better you can focus on finding the root cause. Test/inspect FI grounds, Trigger Point connections, etc.

Testing the MPS electronically is very simple with an ohmmeter. If you have the vacuum pump, that's an easy enough test too.

[injunmort]

fuel sock and fuel filter, first.

[GregAmy]

Another data point.

I was considering hitting the Lime Rock Historics car show today, figured I'd let the 914 decide if we were going. The 914 decided we're not going, it would not start.

Fuel pump cycles with the key, car cranks fine. After a couple revolutions it briefly fires, then dies. I can continue that for a seemingly infinite number of key cycles: key on, pump on, crank, briefly ignition for a few cylinders, dies.

It's not the fuel pump circuit. I jumped between 30 and 87 on the relay plate and the fuel pump is audibly running, car does the same thing: briefly fires then dies. I can also smell fuel so I'm confident I have fuel flow/pressure.

I'm thinking either ignition or something in the engine management. No motivation to deal with this until October. I momentarily considered driving the licensed rollcaged 914 2L race car to this event, but an hour-and-a-half on a race suspension and 13-yr-old Hoosiers just didn't appeal to me. I'll play with the race car next weekend at Palmer (it's getting replacement tires before then).

-GA

Edit: I have neither a spare MPS nor spare CHT sensor to check, so this will need to wait until another day.

[GregAmy]

OK, I lied, couldn't stay away from it. Since I didn't make it to the car show I got the race car prepped and loaded and hit the street car again.

I asked my wife to crank the car over while I shot it with starter fluid, and to my surprise I can keep it running that way. However, stop delivering it the ether and it dies.

I don't have immediate access to a fuel pressure gauge, but I disconnected the fuel delivery pipe in the engine compartment and jumped the fuel pump, and it's delivering a good stream of fuel into my fuel jug.

To remind, I also jumped the fuel pump and tried to start it, same behavior. At this point I'm convinced it's not the fuel pump or control circuit.

How does this affect our thought process? What other failures in the engine management system would cause brief spurts of fuels then lack of fuel delivery?

Man, carbs and basic solid state distributor ignition sound so nice right about now...

[GregAmy]

And more randomly-chucking darts toward a blank wall...

- Disconnected MPS hose and plugged, same behavior.
- Reconnected hose and disconnected electrical connector, same behavior.
- Disconnected TPS electrical connector....car started!

Wha...?

- Reconnected TPS electrical connector...car started.

<shaking my head>

- Let car warm up - recall I don't have the air bypass or cold start hooked up - and disconnected the CHT sensor, engine died.

- Restarted and disconnected the intake manifold temperature sensor, and the engine note picked up a few RPM and seemed to run a tad smoother.

I replaced the TPS board with a Dave Sprinkle unit a couple of summers ago, adjusted with a spare TPS plug and an audible ohmmeter...rechecked it just now and it's fine.

I'm stumped. Is this a component failure or am I dealing with some kind of gimpy wiring harness problem? Don't have the bucks for a new wiring harness just to try it out...dammit.

[injunmort]

i am starting to suspect a duff coil and just for cheap yuks, replace the condenser. both fine sources for intermittent ignition problems. since you have verified consistent fuel flow.