Running on cylinders 1 & 3 only... Options

[AnthraxBird]

Hey guys, new here. My buddy and I are working on a 72 1.7L and it's only running on 1 and 3. Cleaned and checked the trigger points, still no dice. Now, when you unplug the connector for the trigger points, it runs on all 4, for about 3 seconds til it starves of fuel. Input?

[pbanders]

Hey guys, new here. My buddy and I are working on a 72 1.7L and it's only running on 1 and 3. Cleaned and checked the trigger points, still no dice. Now, when you unplug the connector for the trigger points, it runs on all 4, for about 3 seconds til it starves of fuel. Input?

Look at my web page for suggestions. I recommend you test every component in the FI system for basic operation, my page has info on how to do this. For your specific problem, test the trigger points, the wiring harness (both the TC's, grounds, and the injector leads). If you have spares (which everyone who has a nearly 50-year-old car should have (IMG:style_emoticons/default/smile.gif) ), swap in known good/new TC points and ECU.

You might also want to consider buying a noid light for Bosch injection, it visually shows whether an injector is firing or not.

https://www.amazon.com/OTC-7188-Bosch-Noid-...e/dp/B000P72CMW

[AnthraxBird]

Ok I'll look at it. Funny you said that, we have a no voltage issue on the fuel pump, but I suspect it's the relays as they're corroded as hell and falling apart.

[pbanders]

Ok I'll look at it. Funny you said that, we have a no voltage issue on the fuel pump, but I suspect it's the relays as they're corroded as hell and falling apart.

Just checking, I assume you know that the fuel pump is only energized by the ECU for 1.5 sec when you turn the key to the "on" position, right? When you turn the key to "cranking/start", then the fuel pump will turn on while cranking. If the engine doesn't start, and the key returns to "on", the fuel pump will turn off. The only way the fuel pump will stay running in the "on" position of the key is if the engine is running, too.

[TheCabinetmaker]

Turn the plug on the distributor around and see if it runs on 2&4. If it does, you have a trigger point problem. Also if it does, your injector plugs are switched.
One and four fire together. So do two and three.

[pbanders]

Turn the plug on the distributor around and see if it runs on 2&4. If it does, you have a trigger point problem. Also if it does, your injector plugs are switched.
One and four fire together. So do two and three.

Wow, I don't go and look at my own D-Jet site and I forget it all! Cabinetmaker is right about the injection grouping, it's 1 & 4 and 2 & 3. If you're seeing both cylinders 1 and 3 working, then both injection groups from the ECU are working, and I think this also implies that your trigger contact points are working, too. Your issue does not appear to be the ECU or the TC's, leaving the harness, the injectors, and the grounds to check.

[AnthraxBird]

Ok, I thought the opposed cylinder fired at the same time, but it's opposite of what I thought looking at the firing order. Definitely a fuel issue. There is no injector pulse at 2 and 4. I'm just stumped that it runs fine for a brief moment when the Trigger points are disconnected!

Also, the air cleaner isn't connected, as well as the other electrical connections. Could that be an issue?

[AnthraxBird]

Ok I'll look at it. Funny you said that, we have a no voltage issue on the fuel pump, but I suspect it's the relays as they're corroded as hell and falling apart.

Just checking, I assume you know that the fuel pump is only energized by the ECU for 1.5 sec when you turn the key to the "on" position, right? When you turn the key to "cranking/start", then the fuel pump will turn on while cranking. If the engine doesn't start, and the key returns to "on", the fuel pump will turn off. The only way the fuel pump will stay running in the "on" position of the key is if the engine is running, too.

Yessir. No power at all on the pump.

[TheCabinetmaker]

Did you check the fuse on the relay board?

[AnthraxBird]

Did you check the fuse on the relay board?

My buddy said he did, but maybe I should check. That's the board in the engine bay behind he drivers seat correct?

[TheCabinetmaker]

Yes. The fuse to the rear is for the pump. There is also a relay there for the fuel injection. I "think" its the middle one. Don't just look at the fuse. Roll it in its holder or take it out and check it with a meter. Check the holder for continuity too.

[pbanders]

Yes. The fuse to the rear is for the pump. There is also a relay there for the fuel injection. I "think" its the middle one. Don't just look at the fuse. Roll it in its holder or take it out and check it with a meter. Check the holder for continuity too.

+1

If the relay and fuse are good, check to make sure you're getting 12V to the board for 1.5 seconds when you turn the key to "on". The relay boards are old and the undersides are often in poor shape, as well as the connectors. If it were me, I'd start at the ECU fuel pump relay pin (#19), and trace it until you find where it goes open.

[TheCabinetmaker]

Did you turn the plug on the diz around? Until you do that you have not ruled out the trigger points or the injectors. If the injectors on one side are plugged in wrong you could get 2&4 firing together.

[pbanders]

Did you turn the plug on the diz around? Until you do that you have not ruled out the trigger points or the injectors. If the injectors on one side are plugged in wrong you could get 2&4 firing together.

+1

Cabinetmaker is my new troubleshooting guru, he's thinking of all the things that happen when PO's have their hands in 50 year-old cars.

[TheCabinetmaker]

Thanks Brad. I've managed to keep my djet going for 43 years. Learned a few things along the way. Most of it from reading and studying on your site.