My wife's 91 Honda Civic DX manuel tranny starts and idlles on aux injector no fuel comes out of main. Good fuel pressure and new injectors no help. Does this mean the ecu is bad?

More likely the wiring is at fault on a car this old... is the ECU flashing out any codes?

. Perform K-Test on the ECM (search archives).

. Replace the Ignition Control Module (ICM). Apply silicone heat transfer compound to the back of the new ICM.

Thanks Ecu Flashes 1,14,16

Main injector has power to both leads when engine is running but doesn't pulse
I can run a jumper to y/b wire and pules it and injector fires

Those are O2 sensor, Idle air control valve and injector codes.

Here is a nice explanation of each of the codes And what might be the cause of most of them.

ECU codes, code , explanation - Honda-Tech

Thanks Smoothy It just doesn't make sense. Something has to make the injector pulse when you apply the gas. That where the problem is

It originates from the ECU, which will get en error if it doesn't see a load... you have three problems that can be electrical in nature... I'd check all your connectors to start with un plug and replug everything.

I honestly can't remember if they share any of the blukhead connectors and I forget where I put my wiring diagrams I used to have for these.

Once upon I time I did completely fabriicate the entire underhood harness on one of these including rewiring for a different ECU... but its been a lot of years. When I swapped in a B-series engine into a Civic DX , Because the B series was multipoint fuel injection (four injectors) and your DX like mine only had the two fuel injectors similar to a throttle body fuel injection.

If you have a Digital volt meter, I would trace out and check the continuity of those three circuits end to end before you assume its an ECU error. WHich not surprisingly... can tell you if it detects an error in itself... its far from perfect, but it can do it.. ODB2 systems do it far more efficiently. But these ODB0 systems can still help tell you a lot.

Thanks
Looks like we are in for some rainy days will try to check it out this weekend

I hesitated to say swap out the ECU because with electrical items such as that... are usually non-returnible items, not sure what a parts store charges for one of those but junkyards want Roughly $50 for that particular one. And they usually offer a 15 day or 15 feet warranty... whichever comes first, usually the 15 feet from the cash register.

Its not something most people would want a spare floating around for. Or to take the loss trying to recover something auctioning it off on eBay.

But that's the next step if you find good connections in the wiring.

Unfortunely we live in the country, not a used one available within 150 miles. Not sure what I'll do next. Really appreciate all the info.

He's a suggestion...

Car-Part.com--Used Auto Parts Market

You can have them ship one to you.

Thanks that's a neat link. I followed your advice and traced down the wires. Behind the fuse panel is a small grey box call a integrated control unit. It's fried. I've ordered one.I now wonder what cause it to fry?

Look for frayed wires... or places where mice may have chewed the insulation off. Particularly if the car has set idle for an extended period.