Intermittent Problem with Betty's car, I am at my wit's end on this one. Options

[ClayPerrine]

Since the problem is related to the charging system I would swap in another regulator before pulling the alternator. Why did you change the alternator to begin with?

I changed the alternator because it stopped charging. Before I changed it, I did a full field test on the old one. It would not charge even then.

Fro those that don't know, you can jump battery positive power to the field wire on the alternator. That will cause the alternator to charge max output. Don't do it for long, because you will burn up the battery. But it is a good test to see if you have a bad regulator or a bad alternator.

Thanks to everyone who offered suggestions on this. I appreciate the help.

(IMG:style_emoticons/default/smilie_pokal.gif)

[ThePaintedMan]

That's why I suggested looking into the charging system early on in the thread... Glad you found it...hopefully

[r_towle]

What a saga, hope this is the cure.

[timothy_nd28]

I'm late to the party here, glad it's working at the moment. I'm having trouble on how the alternator would cause the Ljet to quit working, seems unrelated (IMG:style_emoticons/default/confused24.gif)

[Cap'n Krusty]

Both D-jet and L-jet require a minimum voltage, and the voltage needs to be pretty constant.

The Cap'n

[Cap'n Krusty]

Oh, it's around 11v, maybe 11.5, IIRC. Been a while since I looked it up.

The Cap'n

[timothy_nd28]

100% agree with you on the low voltage situation, but he re-started the car every time the engine cut out. If the battery was going flat, enough to drop out the Ljet, then he would of needed a jump every time, which is a detail that I didn't read in the earlier posts.

[Dave_Darling]

Oh, it's around 11v, maybe 11.5, IIRC.

I know from personal experience that the D-jet will work pretty decently until the center console voltmeter drops below 9V. I don't know what the actual system voltage was, but when things got low enough the engine would die every time I hit the brakes. It also cut out in time with the lights when I used my turn signal.

I almost made it home that time... Got about a half-dozen blocks away and then a light turned red just before I got to it.

--DD

[ClayPerrine]

Oh, it's around 11v, maybe 11.5, IIRC. Been a while since I looked it up.

The Cap'n

Cap'n,

The alternator is charging. I get 14.1 Volts at 2k RPM when it is hooked up. I suspect it is a blown diode causing a reverse voltage spike.

[Bartlett 914]

Is the belt tight? Is the alternator well grounded?

[Dave_Darling]

I suspect it is a blown diode causing a reverse voltage spike.

You've got an O-scope, don't you? Time to check the voltage with it!

--DD

[ClayPerrine]

I suspect it is a blown diode causing a reverse voltage spike.

You've got an O-scope, don't you? Time to check the voltage with it!

--DD

I also have a freshly rebuilt alternator that was already scheduled to be installed on her car tonight. (IMG:style_emoticons/default/biggrin.gif)

[r_towle]

I suspect it is a blown diode causing a reverse voltage spike.

You've got an O-scope, don't you? Time to check the voltage with it!

--DD

I also have a freshly rebuilt alternator that was already scheduled to be installed on her car tonight. (IMG:style_emoticons/default/biggrin.gif)

the one real man repair on these cars is the alternator in place...

rich

[57lincolnman]

About 2 weeks ago, Betty came home and said her 74, 1.8L Ljet 914 was intermittently cutting out. I took it out to test drive it, and sure enough, it will randomly cut out. Sometimes mildly, sometimes it feels like the engine shuts off completely, then turns back on.

So I started troubleshooting.

Nope, grounds for the injectors are fine.

Put the LM-1 in the tailpipe and had her drive it. Every time it cuts out, the LM-1 shows it going lean. I put an L-Jet tester I have on it and ran through all the tests and it shows as working fine. I had it running in the garage, and I went through a "wiggle test", wiggling every wire and connection on the engine. Nothing I do can replicate the issue in the garage.

So I started throwing parts at it.

To date I have replaced:

The air flow meter.
The fuel injection wiring harness.
The double relay.
The dropping resistors.
The fuel pump.
The ECU.
The CHT.
The whole distributor with a different pertronix, and tried points too.


Nothing I have done to date helps. So I am hoping the collective knowledge of this place will help. I have checked all the simple stuff already. This is going to be hard to fix, whatever it is.


I am now to the (IMG:style_emoticons/default/WTF.gif) stage, and looking for suggestions.

[57lincolnman]

Sort of late to this discussion but I had a cut out problem similar to what you describe. It was the temperature head sensor. It was not seated properly causing it to cut out. I tried similar things but once I replaced that, the car ran fine. If you still have problems, you might want to look at that.

[malcolm2]

Will we be seeing a FS post from you soon? You have lots of spare parts now, that's for sure.

Hope you found it.

As I remember, it is a good feeling.

[Dave_Darling]

I also have a freshly rebuilt alternator that was already scheduled to be installed on her car tonight. (IMG:style_emoticons/default/biggrin.gif)

I'd still suggest checking the voltage with an O-scope. It will give you more confidence that the alternator was the problem--and will tell you what kind of problem it was.

--DD

[rick 918-S]

Relay board failing.

[ClayPerrine]

Will we be seeing a FS post from you soon? You have lots of spare parts now, that's for sure.

After almost 30 years of owning and working on 914s, I have LOTS of spare parts. I buy up the L-Jet fuel injection parts as soon as I can, because they are getting rarer. I also have lots of heater parts, engine tin, and windage trays too.

I even have bus alternator harnesses that were mis-labeled as for a 914. They have a pigtail off the 3 pin connector to hook up the charge light circuit. They would be perfect for someone with carbs who wants to eliminate the relay board.

[rgalla9146]

A little late and a bit off topic but.....
Disconnect the alternator and run the car ?
Doesn't that damage the alternator ?