Vehicle was running great until I lost cylinder no. 2! Verified spark was good. Hmmm... must not be getting fuel. Swapped injectors with one of the good cylinders and was happy to see the issue moved with the injector.

I guess I'm going to shell out to have them all cleaned again. Even though I just did that less than 3000 miles ago. I say all because when I unplugged the injectors individually with the motor idling, each had varying effects on how it ran. So some of the others in addition to no. 2 may also be dirty?

But what could have caused them to go bad all of a sudden? One day it was good, but then the next day when I go to take it to work it's crap. I have read that letting the fuel level get too low can dislodge crud in the tank. It had about 3 gallons in it last time it was running well and it has certainly ran on less fuel than that before. Should the filter be replaced? Is it worth taking the tank out and cleaning it?

Lots of questions, but I am happy the immediate issue presented itself so quickly. I'm just trying to diagnose the root cause to avoid another $100 injector cleaning/test.

A good clean filter is really important,your pump will be damaged and your injectors....well you have found that out.
Take your sender out of the tank and have a look around if its full of crap sort it ,these tanks do rust because many of these cars have been parked up for yrs with an empty tank....that's the issue.
Keep good fuel to the pump,really important (again) ok.

I wouldn't base too many assumptions on one tank of gas. Go to a different Chevron, give it 100 miles, then reassess injector problems.
Also ethanol could be eating the rubber hoses, which would cause injector problems.

I've been using Chevron Fuel Injection cleaner in my P-cars fuel systems and to clean/soak individual injectors for many years. To clean an injector, soak it in the cleaner with the injector tip up. I've been amazed how much dirt will drop out of the fuel line end of the injector.

With the wires and connectors pushing 50 years on these cars, I would turn your attention to exactly that. Intermittent problems sounds electrical, atleast to me. I would buy 4 new injector connectors that have wire leads, and replace your old ones.

I ran into a fuel problem recently on my way home from Florida. I did the big sin of getting gas at a station that had the tanker filling the station. A few miles down the road and the car shook stuttered and died. It was from bad gas. The tanker can mix up crap and water. Now I have a bad fuel pump also. I plan on pulling the tank and cleaning.

I have a new set of connectors sitting in a box somewhere. It's not intermittent, but snuck up relatively suddenly. I unplugged the injector in question with the engine idling and it was getting a steady 12 volts on both connections. I'll go ahead and replace those connectors for good measure anyways.

I'm going to try soaking the injectors in that Chevron stuff to see if I can save myself from getting them professionally cleaned again. Is there any way to spray some carb cleaner or something through them as well?

I will say that I have never used anything other than Shell Nitro+ gasoline or whatever their highest octane rating is called.

I'm going to take a good hard look at the tank as well. I'm hoping to get some time next weekend to think about pulling it.

I am pretty sure that the ECU provides a steady 12 volts to the injector. It then gives a pulse to ground on the other terminal to activate the injector.

No. The injectors get a pulsed signal<3V. 12V will kill them. Ground is constant. If you are getting crud in there plugging the injectors it's not a bad injector. It's bad fuel or corrosion in your fuel fystem . A good fuel filter should prevent that.

I did some research on this. I have a bosch book that says they get 12 V but there's a resistor somewhere to drop it down to that 3ish V range. Jeff, I know you're probably one of the best sources for this. Is that resistor integrated into the injector itself or somewhere else in the harness? I was getting the 12 V reading right off each of the two prongs on the pig tail connectors to ground.

I pulled the tank this weekend. There's a decent amount of surface corrosion in there. And it looks like something took a dump in my filter. Just ordered the POR15 fuel tank repair kit. I imagine that's where the issue came from. I'll post up some pics soon.

Leave the por15 kit alone. Remove the corrosion and keep the tank topped off. Add some mmo- marvel mystery oil with each tank of gas.

The power resistors to drop the voltage to the injectors are inside the ECU.

Keep in mind that measuring voltage on a circuit that uses a resistor to drop the voltage will measure the full voltage when open circuit, but will measure correctly under load. It's entirely possible you measured 12V on the injector wiring with the injector unplugged. Remember, no current flow, no voltage drop.

Gary

Ok, this makes me feel a little better. I'm fairly certain on that steady 12 V reading. The injectors all are within spec for the resistance (think it's 1.6 ohms iirc) so I don't think anythings fried.

mepstein, I was using the MMO for awhile but haven't been the last maybe 2k miles. The POR15 is already on its way so I think I'm going to use it just to get my money's worth. Unless y'all know of any damage it can do?

Here's some pics of the tank so you can judge for yourself.





The "garage"...



And one without the cover.



PS can anybody tell me what this plug on the driver side of the rear trunk goes to? I presume it's for some optional component I don't have...

D-Jet injectors should measure about 2.4 ohms.

The rear trunk plug is for the CA-only model accessory CAT light indicator relay/probe.

Some people love POR15, some people hate it. I think it's all in the prep. I've done two gas tanks, and one turned out well, and the other not so much. I'm pretty sure I was rushing the prep on the second one (had to get to a kid's sporting event or something...). The one that DID turn out well I've been running for several years now with no issues.

Take your time and really follow the instructions closely. Do your best to agitate the tank and knock as much of the loose rust and tar off as possible. If you do it right, it should work well (IMHO).