Engine Cutting Out Again, Severe Miss Options

[PDXBob]

Hi 914’ers,
This is a revival of my old post about the same engine cutting out problem on my 1975 914 (1.8L). It cuts out generally after warmed up and driven for a while. Usually happens under load, like when I’m going up a hill. Doesn’t miss on idle or when I rev it up in the driveway. Based on the work I’ve done so far I’m now thinking must be fuel related.

Here’s an (unfortunately) long list of what I’ve checked or replaced:
- new Spark Plugs and wires,
- new 123Ignition distributor, coil and distributor cap
- no vacuum leaks, all ground wires appear in contact and good shape.
- ECM wiring appears good and I’ve tried wiggling its wires to see if any faults
- Tested the TPS and it’s good, also AFM flap moves smoothly.

A couple of other interesting things- I didn’t drive it for about 2 months, and after installing new distributor it ran great for about 2 weeks. Also, on Friday it was cutting out bad, then I stopped at a store for about 1/2 hour and when I restarted and drove home the cut out had disappeared.

So, I’m now think fuel system related.
Any ideas would be greatly appreciated!
PDXBob

[Bruce Hinds]

Hi 914’ers,
This is a revival of my old post about the same engine cutting out problem on my 1975 914 (1.8L). It cuts out generally after warmed up and driven for a while. Usually happens under load, like when I’m going up a hill. Doesn’t miss on idle or when I rev it up in the driveway. Based on the work I’ve done so far I’m now thinking must be fuel related.

Here’s an (unfortunately) long list of what I’ve checked or replaced:
- new Spark Plugs and wires,
- new 123Ignition distributor, coil and distributor cap
- no vacuum leaks, all ground wires appear in contact and good shape.
- ECM wiring appears good and I’ve tried wiggling its wires to see if any faults
- Tested the TPS and it’s good, also AFM flap moves smoothly.

A couple of other interesting things- I didn’t drive it for about 2 months, and after installing new distributor it ran great for about 2 weeks. Also, on Friday it was cutting out bad, then I stopped at a store for about 1/2 hour and when I restarted and drove home the cut out had disappeared.

So, I’m now think fuel system related.
Any ideas would be greatly appreciated!
PDXBob

I fought a similar problem for a long time and I didn't figure it out until it got so bad it wouldn't run. Turned out to be the ignition switch. I actually put in a remote switch rather than replacing the ignition switch since I leave it with the top of a lot.

[emerygt350]

Very interesting, I was going to say coil related (they can become heat sensitive) but anything that causes a drop of power reaching the coil would have the same effect. Does your tach behave strangely when this is happening?

[VaccaRabite]

Yeah, its not as likely to be fuel. It sounds like an electric problem. Instant cut outs are almost always bad electrical somewhere in the system.

Zach

[burlybryan]

A friend had a similar issue and it was the coil. Surprisingly it was a replacement Bosch that had tested good, but would cut out under high rpms.

[GregAmy]

Similar. Even had to have it towed home once.

It was the round relays, specifically probably the one for the fuel pump.

My resolution was to remove all of the relays and take a razor blade and GENTLY pry the male quarter-split pins apart just a tad, to get better contact within the pin holes. You can feel how they sit tighter in the plate now. Small pipe cleaner to clean out any corrosion in the female pins. Added some dielectric grease and it's been perfect since.

I eventually replaced all the relays with 914 Rubber versions. If you go that way I do still recommend cleaning the female pins and some dielectric.

https://914rubber.com/black-5-pin-multi-pur...lectrical-relay

[L-Jet914]

Similar. Even had to have it towed home once.

It was the round relays, specifically probably the one for the fuel pump.

My resolution was to remove all of the relays and take a razor blade and GENTLY pry the male quarter-split pins apart just a tad, to get better contact within the pin holes. You can feel how they sit tighter in the plate now. Small pipe cleaner to clean out any corrosion in the female pins. Added some dielectric grease and it's been perfect since.

I eventually replaced all the relays with 914 Rubber versions. If you go that way I do still recommend cleaning the female pins and some dielectric.

https://914rubber.com/black-5-pin-multi-pur...lectrical-relay

The fuel pump for the 1.8's is powered by the dual relay that mounts to the battery tray.

[PDXBob]

Very interesting, I was going to say coil related (they can become heat sensitive) but anything that causes a drop of power reaching the coil would have the same effect. Does your tach behave strangely when this is happening?

Thanks for response! No, tachometer does vary when cutting out.

[PDXBob]

Similar. Even had to have it towed home once.

It was the round relays, specifically probably the one for the fuel pump.

My resolution was to remove all of the relays and take a razor blade and GENTLY pry the male quarter-split pins apart just a tad, to get better contact within the pin holes. You can feel how they sit tighter in the plate now. Small pipe cleaner to clean out any corrosion in the female pins. Added some dielectric grease and it's been perfect since.

I eventually replaced all the relays with 914 Rubber versions. If you go that way I do still recommend cleaning the female pins and some dielectric.

https://914rubber.com/black-5-pin-multi-pur...lectrical-relay

Thanks. I’ll probably replace all relays. As a 1975 year car some of them may be 50 years old!

[PDXBob]

Similar. Even had to have it towed home once.

It was the round relays, specifically probably the one for the fuel pump.

My resolution was to remove all of the relays and take a razor blade and GENTLY pry the male quarter-split pins apart just a tad, to get better contact within the pin holes. You can feel how they sit tighter in the plate now. Small pipe cleaner to clean out any corrosion in the female pins. Added some dielectric grease and it's been perfect since.

I eventually replaced all the relays with 914 Rubber versions. If you go that way I do still recommend cleaning the female pins and some dielectric.

https://914rubber.com/black-5-pin-multi-pur...lectrical-relay

The fuel pump for the 1.8's is powered by the dual relay that mounts to the battery tray.

Yes, I hope it’s not the dual relay- kind of $$$$. Anyway to test? I may take it out, clean and see if I can test. Thanks.

[Dave_Darling]

The 1.8 does not need any of the round relays to run.

I think I would start wiggling wires while the engine is running to see if any of them make it stutter or stall. Bad/loose connections or broken wires can do that.

Have you looked in your fuel tank? Debris in there can clog the pickup, then when the pump stops running it can sink back down to the bottom of the tank. (Don't use a match; have a fire extinguisher nearby!)

--DD

[Artfrombama]

Missing under a load is usually point gap too narrow (electronic, not this) or fuel starvation. Fuel filter, pinched fuel line or low fuel pressure

[wonkipop]

i agree with dd and artfrombama.

i reckon its fuel.
either a looped hose is collapsing at a bend or there is a problem at the tank.
sock in tank? even a fuel filter - dunno if you have checked the filter, maybe you have.

typically this tends to happen after you have had it running a while.
debris builds up,
the car calls for fuel under load and it all chokes up.
or alternatively a looped hose which has aged a bit collapses under demand for the fuel and strangles off supply.

(IMG:style_emoticons/default/beerchug.gif)

[Artfrombama]

Similar. Even had to have it towed home once.

It was the round relays, specifically probably the one for the fuel pump.

My resolution was to remove all of the relays and take a razor blade and GENTLY pry the male quarter-split pins apart just a tad, to get better contact within the pin holes. You can feel how they sit tighter in the plate now. Small pipe cleaner to clean out any corrosion in the female pins. Added some dielectric grease and it's been perfect since.

I eventually replaced all the relays with 914 Rubber versions. If you go that way I do still recommend cleaning the female pins and some dielectric.

https://914rubber.com/black-5-pin-multi-pur...lectrical-relay

The fuel pump for the 1.8's is powered by the dual relay that mounts to the battery tray.

Yes, I hope it’s not the dual relay- kind of $$$$. Anyway to test? I may take it out, clean and see if I can test. Thanks.

Send it to me, I'll stick it in my car and give it a shot N/C. PM me

[ClayPerrine]

You may think this silly, but pull the passenger seat and see if the seat belt interlock crap is still there. It has a thin black wire that goes from the unfused side of fuse #8 to the interlock logic relay. If that wire is out of the connector and bouncing on the floor, it will cause the ignition to cut out. The symptoms you describe fit that problem.

It could also be an issue with the seat belt interlock logic relay itself. Either way, the solution is to drop the fuse block and cut the wire free from fuse #8. Then it can't short out.

[PDXBob]

You may think this silly, but pull the passenger seat and see if the seat belt interlock crap is still there. It has a thin black wire that goes from the unfused side of fuse #8 to the interlock logic relay. If that wire is out of the connector and bouncing on the floor, it will cause the ignition to cut out. The symptoms you describe fit that problem.

It could also be an issue with the seat belt interlock logic relay itself. Either way, the solution is to drop the fuse block and cut the wire free from fuse #8. Then it can't short out.

Thanks Clay. I never considered seat belt interlock “crap”. One more thing to add to my list.

[PDXBob]

I’ve been working on my bad cut-out/miss, and am redoing a few of the ground wires that seemed a little frayed. One thing I’ve noticed is that F.I. Wiring is “brittle”, and not the good kind of brittle, as in (peanut) brittle.

As some have suggested, I’ve tried jiggling FI wires while idling, and it doesn’t cut out then, but this harness may be on its last legs- 50 years old. May have to inquire about cost of good used FI harness. Hate to just continue to replace parts without knowing the root cause of my cut-out/miss problem though.

I still need to check out a lot of things you all have suggested.
Thanks again for all of your ideas!
PDXBob

[mgphoto]

What I personally found is that the issue is electrical, fuel or ignition, if the engine back fires then it’s ignition as fuel is still being introduced into the cylinders if there isn’t any back fire than it’s fuel interruption. Most often it’s something simple like a loose connection, you mentioned that the engine ran fine after you installed the 123 dizzy, that is a clue. Good luck.

[emerygt350]

What I personally found is that the issue is electrical, fuel or ignition, if the engine back fires then it’s ignition as fuel is still being introduced into the cylinders if there isn’t any back fire than it’s fuel interruption. Most often it’s something simple like a loose connection, you mentioned that the engine ran fine after you installed the 123 dizzy, that is a clue. Good luck.

There is an exception to this... the combination of the two. When your TPS malfunctions the ECU cuts all injectors, so an electrical issue resulting in a fuel issue and no backfire...