Thread: Injectors not flowing? Verify without pulling fuel rail?

I'm trying to avoid pulling the fuel rail, and am looking for suggestions. I discovered that my new build (still in progress) is only running on cylinders 1/4. I was using a laser thermal probe to check the temp on the thermostat, and for fun was hitting other places while it was warming up. Discovered that there was no heat on cylinders 2/3 on the header, 1 and 4 were both warming up quickly.

Pulled plugs on 2/3, they didn't have soot, but had a baked on residue that didn't look right, so replaced all 4 with NGK. No change.

Pulled the distributor, rotated manually to hear injectors ticking, all 4 ticked as they should. (Had to remove the fuel pump relay as it also ticks, and I think the AAC solenoid on the intake manifold) I had checked this before and they were fine, also checked resistance previously and they were all in the normal range, can't remember exact resistance values at the moment though.

Checked spark on all 4 plug wires, all good.

So, everything comes back to those two injectors being clogged. I'm trying to avoid pulling the fuel rail, anyone ever troubleshoot something like this and have any advice to offer?

when i first fired my motor up, all 4 injectors were clogged with old stale fuel. my mechanic "gently" tapped the metal caps over the injectors with a hammer. bingo.

Problem solved. I was listening to them tick, and a friend asked what order they were firing in. I told him it was 1-2-3-4. He checked and said they should be firing 1-3-4-2. I should add here that I had spliced the low port injector wiring into my high port harness. Everything seemed to be wired correctly, checking FSMs for the model years involved, and even the color of the injector wires matches my harness. But, I reversed the wiring for 2 and three, and sure enough, that resolved my issue!

I missed some info in my last post, too tired.

I had pulled the spark plugs on 1-3, and rotated the distributor with the fuel pump active. I was expecting to see signs of fuel shooting into 1, and nothing in 2/3. I actually saw no fuel spraying in any of these. I guess the amount sprayed was too little to be visible. I could smell gas though from all cylinders, so I knew something was happening.

When I was listening to just the injectors, and rotating the distributor, it really sounded like they were firing in the order 1-2-3-4. They are so close together, it can be hard to tell. I ended up unplugging #2 and then separately #4 and listening as I made them tick, and that was when I realized the firing order was actually 1-2-4-3. Once I heard that, it was clear that 2/3 were somehow reversed. Again, despite the wire colors matching my high port harness.

Glad you got that figured out! Keep moving forward. Good job.

Always 1-3-4-2, 1-3-4-2, 1-3-4-2. Same sentiments as above. Glad it is fixed and now forward moving time.