I hope I'm putting this in the right area, if not I apologize.


I recently resurrected a 1987 Wagoner Limited, 4.0 I6 from 4 years of sitting in a field. Runs surprisingly well but has one little hiccup, it doesn't like to start on a hot day. IAC, TPS are new, I cleaned the injectors and TB,replaced fuel pump, filter and tank (empty for 4 years was a rust tank). I haven't done the CPS yet only because other than hard crank the symptoms just don't seem to be there.


To start it on hot days after its been sitting I need to floor the accelerator and it'll sputter to life. Once it starts it'll run great and start with a little difficulty unless it sits for a few hours, then I'm back to the flooring part. Once I couldn't get it to start at all after 10 hrs of sitting in the lot at work, towed it home, 1hr or so later it fired right up. I've read almost everything I could find about cps failure, ignition module, fuel injectors,etc. Fuel regulator pressure when idling is 31ish and 39ish with the vacuum line disconnected.


Attached is a picture of my ignition module there appears to be some corrosion around it, could that hamper spark particularly when its hot?


As for the CPS, any advice on getting it changed, I can get my massively extended socket onto the lower bolt but not the top bolt, maybe a technique I'm missing.

Sorry for the great wall of text, this is my first time working on something beyond an oil change.


Thank you for any/all help.

 

As far as cps goes you'll need a wobble or swivel to get at it. Also lowering the front drive shaft can help get you some clearance also. That IM is definately corroded, take it all apart and clean it with electronics cleaner and a stuff bristle brush. I wonder if your getting into some type of vapor lock have you checked fuel pressure at the rail when it's hot out and your trying to start it?

 

I haven't tried on a hot day when it won't start, this weekend is to be right toasty so I'll give that a shot and clean that IM tonight. Thanks

 

Click on my link below and do posts 1 through 5, and possibly 27.

Post 7 will help you diagnose the CPS, and offers suggestions to help make sure the new one puts out a stronger signal.

 

If you DO go after the CPS, this might help;

To change your CPS I found if you BACK the fronts onto ramps, you won't have them in the way, where you need to lay. A stand under the left front frame would be in your way.

If CPS itself is putting out less than .35 Volts AC, unplugged, while it's cranking with a good battery, or the resistance is not 200 ohm's plus/minus 75, hot;

11mm socket > 3 inch extension > universal > long (18-24 inches of extension). Your feet are sticking out under the passenger side, you can reach up past the front drive-line with your left hand to hold the CPS from the front. Your right hand is on the ratchet way back by the tranny cross member. If you tie a long string on the old plug, you can use it to haul up the new. Toss that piece of plastic if it's still there, and do not drop the bolts in there! Echlin # CSS980, (from Napa, for 87-90), should be fine, but some prefer to go to Jeep. I wouldn't bother with anything else for that. Edit..There is a "new" CPS on the scene, Rock Auto #PC307. I just got one, shipped, $36

If your left forearm is bigger than a quart Mason jar, you might consider removing the front drive-line. Also You might cut your old CPS wires if they go through a deal on a bell housing bolt, then be sure your new are held somewhere safe.

The second one is REALLY easy!

 

Thanks that's a good collection of info, but you probably already know that. I'll certainly put it to use.

 

Excellent starting point....

 

I followed the cleaning/servicing and ground replacements covered in Cruiser54's link (1-5). The Jeep has been running and starting great, all week, still haven't replaced that CPS, haven't seemed to need to anymore but I'll keep it around JIC.

Yesterday my wife took it to work, the afternoon temp hit 90deg and when she went to leave it wouldn't start. She popped the hood, waited about 5 seconds, tried again and it sputtered to life.

Today she took it on a 2hr round trip with a brief stop in between, towards the end of her trip the temp gauge reached about 210deg, I understand this is normal (?) but I'm not sure I like it. When she got home I immediately went out to see if it would start and it started great, I didn't even need to hit the accelerator, just fired right up.

As for the driving temp, I'm going to flush the radiator first, something I probably should have thought of much earlier on but hey, its my first project. Also saw some pretty nifty looking home done hood vent jobs.

I really don't understand the "starts fine at 200deg, doesn't want to start at 90deg".

Thanks again folks.

 

First off, I'm happy to see that the tips helped.

Test the CPS per post 7 at 90* and report back please.

Consider post 27......

 

Normally you would never depress the throttle to start it. Just turn the key.

 

I'm not sure why you don't like 210*. That is perfectly normal, at least for later models, don't know about Renix.

 

Renix also.

 

Will do, also already planned on doing #27 this or next weekend.

 

I would do #27 for sure.