In reply to ¯\_(ツ)_/¯ :
I’m still going with a driver issue in the ECU, especially since you said it seems to affect the same 2 cylinders. Is it batch fired?
In reply to ¯\_(ツ)_/¯ :
I’m still going with a driver issue in the ECU, especially since you said it seems to affect the same 2 cylinders. Is it batch fired?
IDk, guess it depends on if you have solid metal motor mounts ;)
In reply to Pete Gossett :
It is batch fire, but #1 and #4 appear to be in different batches (1-2, and 3-4).
¯\_(ツ)_/¯ said:In reply to Pete Gossett :
The bad OEM injectors won't do anything. Bad Tomcos will spray until they heat up, then stop.
When you say heat up, how heated up are we talking? Like normal operating temp, or “dang, that this pretty hot!”
Electrically the injector has a solenoid in it, an electromagnet. Environmental heat can screw up its operation until it cools down- this almost sounds like what your Tomco injector is doing.
And as others have pointed out, they may be drawing too much current and heating up internally to the point of failure.
Your observations of the Tomco injector seemed like an “Aha!” moment to me :-)
*Edit- the decapitated ground seems like a huge find too
In reply to paranoid_android :
Hot to the touch, but probably still cooler than they could potentially be under the hood after a few hard back to back 3rd gear pulls. So that would suggest either a wiring issue or airflow? I would love for the solution to this to be "cut more holes in the hood."
The failed Tomcos would work again if I let them cool down, but I could get them to stop firing by driving the car hard for a minute or so. I should really get a non-contact thermometer.
I had an issue with the C4 that might add info/help. I put a brand new out of hte box set of Accel 24lb injectors. I had 3 that wouldn't fire. Apparently two of the new injectors (one on each bank) had too much resistance and pulled all the power from the single driver on the ECU (batch fire) that it literally kept the others from firing. That took way too long to discover.
TLDR: check your resistance?
I’m totally guessing at the wiring for the injectors here. If 1 and 2 are batch fire, and 3 and 4, that means the ECU sends an output to each group separately? Like this?
If this is (remotely) accurate, it seems an issue with the ECU would be killing the injectors in the same batch instead of two separate batches.
Based on that sketch I’m not convinced mismatched impedances across all the injectors would even cause an injector failure.
Crappy connections to each injector or injector to ground might do it though.
In reply to paranoid_android :
Yeah, your drawing is roughly my understanding of it. I need to see how the grounds are shared though, as that could lead to weird stuff if the ground wires and power wires are paired differently.
EDIT- here's some guy's possibly wrong diagram, I guess we assume that all the magically connected positive wires actually run through the ECU:
That would be how Toyotas and Megasquirt are wired. One leg of the injectors goes to B+, the other goes to ground through the ECU. Toyota doesn't batch them. Megasquirt can.
Bosch derived systems pulse the ground side of the injector, as indicated in the diagram above. Therefore a bad processor ground is always a suspect. Positive current is a constant at the injector.
ECU replaced, ground strap replaced. Went for a drive, #3 injector now dead. Resistance reads 3ohms just like the good injectors, and harness has signal to fire.
New theory: my OEM injectors are all really old, and Tomcos are straight up doodoo garbage. How does that grab everyone?
i say burn it down and start over. just put a 4age in there.
Did you ever check the current or set the injector up in a jar and watch it squirt?
Just so we're clear, my drive cycle for killing the Tomco injectors is just to warm the car up, then do repeated 2nd and 3rd gear pulls until it starts misfiring after 10 minutes or so. I think it's a heat issue for those, and just an age issue for the OEM injectors.
In reply to Dr. Hess :
I have not checked the current, but did fire an injector off into space. The spray pattern on the OEM ones looks better (more misty and less liquid) than the Tomcos.
At this point I would love some recommendations for a rebuild service, or reasons I should spend $500 on a set of Injector Dynamics ones. Unless we still think the wiring/ECU is killing them.
I’ll remember this thread if my Lemons mustang ever gives me E36 M3. Straight to a carb, I have a setup already for that day.
I’m no help unless you need some 23lb injectors from a 5.0, I think 19 are stock.
I also have some 80lb (stock is 35) injectors from when this engine had Megasquirt. Any value in installing or measuring those?
I think at this point I might try to find some more functioning stock injectors as a proof of concept, then order something nicer.
Also, are these worth buying? Too late I said berkeley it and bought them.
I would check the current on the 2 that are failing and compare to the 2 that are not. You have done everything else. And is there a schematic of your actual installation?
In reply to Dr. Hess :
Well, I just had a #3 injector fail, so I think the #1 and #4 thing was a matter of me wanting to see a pattern where there wasn't one. I can still check current though. The above schematic is correct as far as I can tell.
¯\_(ツ)_/¯ said:New theory: my OEM injectors are all really old, and Tomcos are straight up doodoo garbage. How does that grab everyone?
seems like it would be a major coincidence if that was the case. While I can see an aftermarket set being junk somehow, it would be pretty odd for OEM injectors to just all suddenly start to go bad at the same time. I'm quite certain the injectors I run are 25 years old and have never been touched except for the new o-rings and caps I installed.
On the flipside, the Porsche has some no-name ebay injectors in it and has also never had problems. So even with a good collection of old-ass stuff and cheap-ass stuff, no failures for me. I have a hard time believing that even if you HAVE two sets of old-ass stuff and cheap-ass stuff, you would have such a coordinated group of failures.
It's got to be something other than the injectors themselves. I woudl try to blame bad fuel, or debris in the fuel system for it, but seems that's 1) already checked and 2) unlikely to cause such an immediate failure.Plus you don't seem to have the symptoms like a dirty filter or dirty nozzle on the injector.
Have you checked the throttle position sensor? Maybe spiking voltage and causing some kind of overload to the injector electronics?
Relays: On the "from a similar era" Porsche the OEM DME/fuel pump relay has issues where it get hot and shuts down (usually due to overload due to outgoing fuel pump working too hard/pulling too much voltage), and that same relay controls the DME as well. Is is possible you have some kind of similar relay issue? Perhaps jump all relevant relays and do a test drive to eliminate that possibiliy?
Also, came upon something referencing "METAL TO METAL CONTACT BETWEEN FUEL INJECTOR/INTAKE PORT-CORRECTED BY INSTALLING INJECTOR SPACERS (P/N E5PZ-9D905-A)-1985 MERCURY COUGAR; MERKUR XR4Ti SO EQUIPPED" Upon further research, there seem to be multiple technical bulletins that make vague reference to "injector shims" or "injector spacers" - do you have those on your car? Could the failures be cause by some kind of excessive vibration or heat due to direct contact with another surface?
In reply to irish44j :
That last paragraph about direct contact/heat transfer or possibly vibration rings a few bells here. I have never seen an electronic injector with metal to metal contact, thus worth a close look!
My injectors do all have some sort of phenolic or other composite spacer so I don't think that's it. I went through the whole fuel system, that's all clean too. Checked TPS, all in spec, no dead spots.
My meter doesn't have any sort of peak hold function for current, so I could only get an average reading, but at every injector (currently installed are 2x old OEM, one unfailed Tomco, and one Tomco that fails when hot but works currently) I'm reading .03-.04A at a fast idle (needed to keep from stalling when running on 3 cylinders).
TurnerX19 said:Bosch derived systems pulse the ground side of the injector, as indicated in the diagram above. Therefore a bad processor ground is always a suspect. Positive current is a constant at the injector.
There are some oddball exceptions to this rule. Mazda GSL-SE (Bosch L-jet derivative) have a constant ground and the ECM controls injector power. Probably was a translation error because they drive on different sides of the road in Germany and Japan.
RC injectors installed, had to beat on it for a while but eventually developed a miss on #1. Fuel pressure checked fine, injector resistance fine, signal to connector was there- it cooled down and started working again before I could diagnose further.
At this point, I'm interested in what else we think it could be outside the fuel system. I would think distributor cap or rotor would always happen on the same cylinder, same with wires or plugs. How do I have this roving dead cylinder that happens when things heat up?
In reply to ¯\_(ツ)_/¯ :
Have you checked compression or done a leakdown test hot, right after it’s been misfiring?
With your previous distributor woes, have you pulled it recently to check for wear/damage on the drive gear?
You'll need to log in to post.
