Cylinders 1 and 2 not firing

[bmcglone]

With new polished stainless headers, all primaries have turned a nice gold color except cylinders 1 and 2. Engine is unmodified from a 1990 Mustang GT that ran perfect. Good spark and fuel injector pulse to both cylinders. Is there anything else I can test short of changing fuel injectors.

[jayguy]

try swapping injectors to those two if you think that's your problem. Do you have a laser temp gauge you can point at the headers to see if they're getting hot?

Are these new injectors or did they come with a used engine? Could be the injectors just need to be cleaned out or rebuilt. Rebuild kits aren't too bad, and it's not that bad or a process.

Many videos on youtube to show you how to do it.

Good luck.

[bmcglone]

The injectors were in the car. I have a pyrometer I am going to try. If i am swapping injectors, I might as well replace them.

[jayguy]

What I meant by swapping injectors was to move them around the engine and see if the problem moves with them.

It could just be junk in the injectors blocking flow. A rebuild kit comes with new filters, new pintle covers, and new o-rings. We did it a few weeks ago on Ryanh's injectors more as a preventative measure than because they weren't working, and it gives you a chance to test the injectors individually with a 12v source and a momentary switch.

Much cheaper than a full set of injectors.

[bmcglone]

I looked at rebuild kits. I think I will go that route with some bench testing. Does it matter which rebuild kit, Type 1, 2?

[jayguy]

I haven't seen anything about "type 1 or type 2", but I'm not the one who bought the kit.

Ryanh got his kit from fuelinjectorconnection.com. We made our own pressurized fuel system for cleaning and testing with rubber fuel line and a nipple for the air compressor, and connected a 12v power source and momentary switch to the injectors so we could pressurize the fuel, use the switch to open and close the injectors, then we put it all back together once we were done.

Looks like that site also offers injector restoration, where they'll do it all for you.

[1fastsedan]

If you're not interested in rebuilding/testing them yourself, my buddy runs RC Engineering and they do fuel injector cleaning, repair, and calibration.

RC Fuel Injection

[Wade Chamberlain]

how do the plugs on those two cylinders look compared to the rest? How does the car run? If you were completely missing 2 cylinders, it would be pretty ratty. A compression test or leakdown test would confirm or rule out something compression-related (head gasket, rocker adjustment, etc). Check the obvious too....perhaps those two plug wires are swapped?

[bmcglone]

Checked primary temperatures. Cylinders 3 & 4 ~ 650F, cylinders 1 &2 ~300F. I am going to check plugs and do compression a test tomorrow. The engine seems to idle and run fine. There is some light backfiring from that side at low rpm acceleration. I unplugged a fuel injector on the other side of the engine and only had some power loss. The engine still ran and idled fine down another cylinder. Plug wires are new, spark plugs are new, getting good spark (held the boot next to the header with the engine idling). Getting good injector pulse. I am going to order the fuel injector rebuild kit mentioned above. I figure 22 year old injectors, it won't hurt.

[rich grsc]

650F at idle?, that sounds like a lean condition.

[bmcglone]

That was the temperature of the primaries on two good cylinders at idle immediately after about 20 minutes of driving.

[Don Payne]

I had my injectors cleaned and flow tested at this place...local for me. They did a great job and it was only like $15 per injector. Good luck!

Wally's Injection Service
1556 S 300, Salt Lake City, UT
(801) 487-4937

[bmcglone]

Compression check: all cylinder 140-150 psi
Vacuum check: steady 17 inHg
Plugs 1-2: soft carbon fouling
Plugs 3-8: good
Firing order is correct.

Going to send injectors in for rebuild.

From what I know about spark plug conditions, a malfunctioning fuel injector can cause carbon fouling.

[bmcglone]

Magically fixed itself.

Lots more power, primaries are gold now, ~650F.

Still going to send the injectors for rebuild.