Need Help Please !!!

[Grizzley]

I was thinking about your hesitation problem, and it remined me of somthing. My grandfather used to have a 1980 Chevy Citation with a 2.5 that had the exact same type of problem. Sometimes the motor just wouldn't go, the car would still be running, but you step on it from idel, and you get nothing. That got me thinking, wasn't the carburated 2.5 bought from GM, just like the 2.8, or was it the predecessor of the AMC FI 2.5? Anyways, he never did solve the problem (he only had his Citation for 2 years 1980-1982) but I was just thinking that it could help you out. If you tracked down what was making the Citation hesitate, it might be the same fix for yor XJ.

The only engine I know of in the XJ that they bought was the 2.8 Chevy. The 2.5 had 2 cyls. added to the middle and became the 4.0 and was AMC's own design. It wasn't so much that I'd get nothing from idle, it was the fact that it'd die at idle and you couldn't get any spark to restart for about 2 hours. All it had was a monentary spark when the starter first started and one when you turned off the key. Not enough to stay running.

 

[MudDawg]

The weber is a great idea..just be sure to get the 32/36 not the 38 DGEV..for an otherwise stock motor the 38 is too big. If you have room for clearance, toss the junk air filter that comes with weber...get a filter adapter from Redline or K&N and use a larger pleated paper filter. The ignition change is a good idea too...I had the same problem...if you don't have the wiring diagram I can hook you up...you just need a "blue grommet" ford module from any early 80's car.

The 2.5 is a AMC/Renault designed motor...it is the predecessor of the 4.0 the 4.0 has a taller deck to allow for the stroke increase..both motors use the same pistons and rods..when AMC designed the 2.5 they were buying powertrainparts from GM...that is the reason the bellhousing pattern is "small GM" patterned...by the time the engine came into production they had dropped the association...that is why you have a chrysler tranny with a GM bellhousing pattern..yah gotta love Jeeps...

 

[Grizzley]

The weber is a great idea..just be sure to get the 32/36 not the 38 DGEV..for an otherwise stock motor the 38 is too big. If you have room for clearance, toss the junk air filter that comes with weber...get a filter adapter from Redline or K&N and use a larger pleated paper filter. The ignition change is a good idea too...I had the same problem...if you don't have the wiring diagram I can hook you up...you just need a "blue grommet" ford module from any early 80's car.

The 2.5 is a AMC/Renault designed motor...it is the predecessor of the 4.0 the 4.0 has a taller deck to allow for the stroke increase..both motors use the same pistons and rods..when AMC designed the 2.5 they were buying powertrainparts from GM...that is the reason the bellhousing pattern is "small GM" patterned...by the time the engine came into production they had dropped the association...that is why you have a chrysler tranny with a GM bellhousing pattern..yah gotta love Jeeps...

OK, 32/36 got that. The ignition change that I was thinking of just cuts the computer out of the circuit. John (SV1CEC) has the info on his XJ page. Would like to see your conversion to compare the two. A link to a page would be fine. Here's John's:

http://www.m1911.org/cherokee_mods.htm

It's not too far down the page under "ignition".

 

[RichP]

Here is the better of the weber sites to buy from. They have much better support than collins brothers.
http://www.racetep.com/weber.html

As for the filter that comes with the webber it is a K&N filter. Keep an eye on the new one for flooding and follow the directions for setting it up closely. The conversion is a good one, we did it on our 89YJ but also replaced the mechanical fuel pump with a new one that had much higher pressure. We ended up putting a fuel pressure regulator in.
For a lot more webber conversion info do a dejanews search, you'll see a couple of mine pop up but pay attention to Mike Romains responses. He knows these things COLD, we finally narrowed it down to a bad CTO [don't know if older XJ/MJ's have these], it is a thermostatically controlled vacum switch on the intake manifold of the 4.2L motors and if it's not working correctly can wreak havoc on running. It is also a very good idea to replace all your vac hoses now.
The YJ had a fuel filter with three fittings, one supply from pump, one return to tank and one to the carb itself. We initially had the return laying on it's side and that caused problems till we put the retun on top, annoying...

 

[Eagle]

Guys, you're all getting your history a bit mixed up.

The XJ/MJ/YJ 2.5L engine is not a GM engine, it is an AMC engine from the ground up. However, it was not the "predecessor" of the 4.0L. AMC already had the in-line 6 and had been building it in 199 c.i.d., 232 c.i.d. (3.8L) and 258 c.i.d. (4.2L) versions since 1964. The 2.5L engine is that same basic engine with two cylinders lopped off (much the same as a Chevy 4.3 V-6 is a small-block V-8 with two cylinders lopped off). The 4.0L I-6 was just a refinement of the 4.2L engine, it wasn't developed out of the 2.5L 4-banger.

Renault did contribute some development work on the heads for the 2.5L and the 4.0L, as well as working with Bendix to develop the injection/ignition system used on the TBI 4-cyl and the early 4.0L engines.

 

[MudDawg]

Thanks for the heads up Eagle...I will scratch the database I got that incorrect info from...sorry 'bout that..I had good intention.

Grizzley...that ignition mod is fine, will save the expense of buying a new module...same end result...

 

[SV1CEC]

OK, 32/36 got that. The ignition change that I was thinking of just cuts the computer out of the circuit. John (SV1CEC) has the info on his XJ page. Would like to see your conversion to compare the two. A link to a page would be fine. Here's John's:

http://www.m1911.org/cherokee_mods.htm

It's not too far down the page under "ignition".

Grizzley,

Thanks for mentioning my page, but the mod is not mine, there is a link in my page to the original site.

In any case, I would suggest you strip all the wierd things around the engine, like air filter box (with all the associated tubing), the canister, etc. If you need help, please contact me via e-mail.

After that, the Weber is a natural choice, although if I were to redo it today, I might have gone with a fuel injection, for $800, it's only $300 more expensive than the Weber kits and you get all the tools to tune it to your engine and preferences, ignition- and fuel-wise. Check www.customefis.com.

As for the ignition, the Nadder conversion is simple and reversible, you just bypass the original ECM, which by now (after the Weber or especially the EFI install) is not doing much.

At your disposal for any questions.

---------

John SV1CEC

 

[RichP]

The nutter bypass only leaves that part of the computer in place to supply signal to the factory tach. If you don't have a factory tach you can take the nutter one step further and take the comp completely out. It is reversable though, I ran an extra set of wires across from the ECU to the dist and did a neat job of splicing/soldering/shrink tubing on both ends. I also used anphenol connectors on my runs to replace the factory connectors.

FI is the way to go. I also feel that if I had it to do over again on the YJ's 4.2L I would have gotten the Mopar FI kit, that kit has EVERYTHING so that you basically only have to supply a gas tank/fuel source and an engine, no vac lines, no CTO's, no nutter, nothing. talk about a clean install... I never noticed any for the 2.5L though.

 

[old_man]

A classic problem on that engine is the Carter YFA carb. The ground on the automatic choke gets intermittent. You can check it out by using a bread tie to wire the choke butterfly open and see if the issue goes away. I ended up soldering a wire onto the tang that comes out the side/rim of the black plastic choke cover, and tying it to ground. Lots of people rip off the automatic choke and replace it with a cable, like in the old days.

 

[Grizzley]

Bunches of ideas. Got 60 days to sort it out. Didn't make it through inspection. Safety was fine, emissions didn't do so good.

HC GPM actual 4.8 Allowed was 3.20 Fail
CO GPM actual 80.08 Allowed was 80.0 Fail
NO2 GPM actual 4.99 Allowed 7.00 Pass

Definately running rich, black tailpipe, no smoke, just a real strong smell of fuel, choke is wide open also Old Man but thanks for the heads up on that. Rich, it is listed as having a dual CTO in the system. Considering the fuel mixture is controlled by the computer I'm thinking that it could be any number of things that could be sending a bad signal to the computer saying that it was running lean and therefor kicking the mixture up.

John, I agree that a self contained unit would be the way to go, but that's a little steep for me right now. Even for an 84 in this shape. I think it's time to go scrounging in the yards and see if I can find a 4 cyl with the weber conversion on it and buy that.

 

[Eagle]

Grizzley --

After seeing your results, I called "Mr. Carburetor" to ask for his advice. First thing is, he advised NOT to get the Weber. He said it will be very difficult to get that through emissions.

When I read him your test results, his immediate thought was "oxygen sensor." It's a carburetor, so we (I, at least) tend to forget that it's a computer-controlled carburetor, and the computer has to be reacting to something. He suggested trying to find someone with a scan tool that will test the O2 sensor, coolant temp sensor, and throttle position sensor. Knowing how impossible it is to find any scan tool for the Renix-based injection systems, though, I think you should ask the guy at the shop where you had it tested if he thinks an O2 sensor would do the job. When CT reinstated emissions, my '87 MJ 4.0L failed it's first test, and the cause was the O2 sensor.

 

[SV1CEC]

Grizzley --

After seeing your results, I called "Mr. Carburetor" to ask for his advice. First thing is, he advised NOT to get the Weber. He said it will be very difficult to get that through emissions.

Eagle is right, my truck was imported into Greece, before the emission control took effect, so it is registered as a pre-emission control, non-catalytic truck. I can easily pass inspection with those terms, the limits are much higher than the newer cars, but I would never make it into the lower numbers.

Rgds
----
John SV1CEC