JYau

I've done the aluminum valve cover mod. Pretty straight forward but I can add some better pictures here. I would recommend the blue Fel-Pro gasket, it seems to be very high quality and I haven't had anymore leaks.

It turns out the power loss was due to a faulty fuel pump. I have changed the fuel pump and all is fine now.

I was able to replace my fuel pump and motor and that seemed to have fixed my original issue of the engine loosing power when it had warmed up. I used the replacement part Bosch 69302. It was not a direct replacement and required a little improvising to get the pump to fit nicely into the assembly but it can be done. I was able to get the fuel assembly out of the tank without damaging it. I had used some penetrating oil and took my time using a brass punch. I did not need to drop the tank, I was able to do everything that I needed while under the truck. Getting the entire fuel assembly back in was difficult, it requires lining up the fuel line nipple with a rubber grommet fixed on the inside of the tank. I tried for an hour by using touch and feel to get the alignment right but I couldn't get it. I then did the best I could to sneak my phone in front of the fuel assembly and get a picture of inside the tank, only then was I able to get the assembly lined up correctly.

I'm fairly certain I have the 18 gallon tank as my Comanche is '88 SWB 2WD. I read in another thread that only the 16 gallon was used in '86-'87 instead of the 18 gallon tank. And both the 16 gallon and 23 gallon had three tank straps. My tank only has 2 tank straps. Is this correct? I'm going to take my fuel pump assembly out this weekend, if I don't ruin it removing it, I'll probably just replace the pump, otherwise it's a new 4.0 pump assembly.

So I called MTS today and the 2.5 Fuel pump assembly is no longer in production. Now I haven't taken out my fuel pump assembly but it's pretty rusted onto the tank. Does anyone know what my options are? MTS told me that they think the 4.0 and 2.5 assemblies were the same and the pumps were different but they weren't 100% on the assemblies.

I took the TPS out so it would be easier to test so I could get contact to the terminals. Then I connected it to +12V power supply and move the arm full swing and measured the output.

I took out the TPS and tested it, seemed to work normal and was steady. It would swing from no throttle at ~3.85V up to 11.8V at full swing. Any tips on testing the fuel pump?

I have an 88 shortbed 2.5 2WD 4 speed. The engine I don't believe is original, it might be from an 86 and I say this because the oil filter thread is an M20 which I thought was for engines 86 and earlier, can anyone confirm? Anyways, I've had this truck for almost 5 years and has always run great, gets good MPGs and power always seemed smooth for a 2.5. I have done a lot of Cruiser's electrical upgrades etc. to ensure the 36 year old truck continues to run strong. However, today when I was driving it down a 45-50 MPH road the truck started to randomly drop power almost to the point where I though it was going to stall, it's fine at lower RPMs but 2.5k and up it begins to drop very quickly. It might seem to get worse when it's warmed up because one my ride back home after the truck sat for 30 minutes, it didn't start having problems until after a few minutes of driving. The issue seems to only happen under load, with it sitting in neutral I can rev the engine up and hold it there and it seems fine, but this is just a small test So far from what I gathered online, it could be fuel pump issues, MAP sensor, O2 sensor. When I first got the truck, it had a new fuel tank and pump, and I have changed the MAP and O2 sensor just a few years ago. Also, last year the CPS sensor was replaced. The truck starts up perfect every time and idles nice and smooth. Power and acceleration are all normal except when the RPMs and power drops out. When it drops out it bounces back immediately and sometimes will happen a few times and then stop for minutes. I've attached a video for some more context. Anyone have any ideas on what to check? Thanks! IMG_0761.MOV

This ^^^^ I had a very similar problem a while ago and it was all because of the 1 filament bulbs. I took apart almost everything in the rear wiring and couldn't find the issue, it plagued me for a year.

I have done pretty much the same exact thing as you in my 88 MJ. However, my radio that I installed was one from an 87 Grand Wagoneer, the one with a digital tuner. Since the truck had an after market Alpine head unit, the wiring harness was modified and I had to splice the factory one back in. But before I did the install, I had tested the Grand Wagoneer radio to ensure that it worked as expected. I had bought the radio on eBay, and it wasn't tested so I took a chance. Depending on the year of the donor XJ, I would not rely on color codes to rewire, I would carefully look at the pinout diagram and make sure you understand which pin is what. To test the radio, all you need are a few simple tools and a 12V power source, this could be a 12V battery but caution is needed as a battery isn't fused. Follow the sticker label on the radio for the pin functions. You typically hook up the 12V to the 12V pin and sometimes there is an ACC pin that is needed as well. Then you can take a speaker, ideally a 4 ohm one for car audio but 8 ohms will work just don't turn the volume up high, and test each audio channel output. With a few feet of wire, a wire stripper and a few wire alligator clips, you can test the whole thing out. If everything works as expected then the issue is with the truck side of the wiring. If the radio passes the test the next step would be to test the connector that you spliced back in. This would require a voltmeter to ensure that the proper voltages and impedances exist at the connector itself. Start the truck and verify you measure 12V at the 12V pin, turn the truck off and measure across the speakers and verify you see ~4 ohms. Check the grounds and verify they have a good connection. Verify your chassis is actually chassis. From your video the concerning thing is that the LCD clock goes out when you ground that chassis wire. Something is upset when your touching the ground wire. The bracket that the radio unit rests in while installed in the dash should be connected to chassis, does that cause the same behavior? How bad was the melted wiring, did you eradicate all of the melted wires? You might have some other wires that were melted and shorted but you haven't found them yet. If you don't have a multimeter your going to be guessing and checking and potentially damaging your radio in the process. A multimeter is the first tool you'll need to figure this out.

I saw this thread a few months ago and thought wow perfect, I can adjust my tach to accommodate my 2.5. So I finally got around to it this week. However, I turned the pot dial all the way to the left and at idle the needle wouldn't even go into range, it still sat below scale. So then I turned the pot dial all the way to the right and now it is better. It sounds and looks like it might be riding a little high like +500 rpm.

Did you check the trackbar? Also, the stock control arms are pretty flimsy too, not to mention that the bushings could very well be worn and squishy.

Sent, happy to support.

Funny thing, I had just recently installed a new thermostat housing gasket as the old one was leaking a bit. When I went to go fire it up for the first time after the new gasket it didn't start. I was very puzzled because that was the only thing I touched. First thing that I check is the CPS and sure enough it was bad. Ordered a new CPS and it fired right up. Strange coincidence, it almost sent me down a wild goose chase.

I think your right about the location of the carb and it being inline with the fuel line at the carb. I also do believe it is a mechanical fuel pump. When I had my 86 Comanche, I was going to do the same but when I realized how much painful work was involved in changing that little filter I just gave up.