mfpatterson

Just rebuilt our original owner 87 Cherokee Lorado 2 door, 4.0L., auto, AC.

Can someone tell me what each of the 4 relay locations are near the battery? Are these relays all the same? They look identical from the outside but the auto part web sites show several different applications.

I took them out to clean them and put them back in (not the same location because I thought they were the same) and the car started and stalled, I moved the relays around and then found one where the car runs ok. I was thinking of replacing them but not sure what the slots are.

Also the cooling fan doesn't work even when I disconnect the cooling fan thermon switch, the fan is new and I checked it and it works. Could it be a bad relay?

Thanks,
Marc

5-90

Your 1987 is what is commonly referred to as RENIX - that can be a useful keyword when searching, FYI.

Pretty much all of the relays used in the RENIX XJ/MJ are standard Bosch/Hella DIN relays, and they're available pretty much anywhere for ten bucks or so. You should keep a couple in your spares box with fuses and lamps, just to be ready.

The cooling fan relay is on the opposite side of the engine bay, on the driver's side fender liner. The cooling fan not kicking on can also be caused by the failure of the thermal fan switch in the driver's side radiator tank - you can check this quickly by unplugging the switch, turning the key ON (no need to actually start the engine,) and using a jumper wire to connect the two pins in the harness side of the connector you just removed. You should see the fan start right up - if the fan doesn't, check the fan motor for a "short" or "open" circuit. Also, check the fan connector for +12VDC - if you have voltage there, the fan motor tests should suffice. If you do not, replace the relay and retest. It's also a standard DIN relay.

As far as the relay arrangement goes, I need to sort that out myself and post a pic on my site. You may have run into arrangement difficulties because of a blown relay, and happened to hit it in the wrong place (then swapped it around to a location where the engine would run without it.) This is why I have "Known Good - Tester" relays in my toolbox - if I suspect a bad relay, I'll replace it with the KGT and recheck. If it works, I pull out the KGT, pull out a BRAND NEW TESTED relay, and use that. Recheck the KGT and put it back for the next time. A bit complicated, but it's worked for me this long.

mfpatterson

Wow thanks for the info...I can't wait to test out the fan. One more question. What would cause a hard starting? The motor turns over at least 6 times before if fires and then when cold it runs rough for the first few minutes. Once it is warmed up it runs real nice. Engine has been rebuilt and has new injectors and regulator.

5-90

Long starts are typical for RENIX - due to the way the system is set up. This can be reduced by making sure your battery is holding a good charge and by upgrading your mains cables (per reports from the field - not just me!)

RENIX is programmed to not fire the fuel injectors or spark plugs until it counts 300rpm at the crank position sensor (CKP) and gets a valid SYNC signal (camshaft position sensor,) although it can work without the SYNC signal and "guess" until it hits #1 and starts. Yes, RENIX can and will run just fine without the SYNC signal once it's started. Sx of a failed/failing SYNC would be akin to starting your engine after a build with the timing "one tooth off" - but it will smooth out and start after a minute.

As far as the "cold rough" run, check for a vacuum leak at the manifold mating surfaces. Use a 9/16" 'flex' socket to tighten the screws to 19-21 pound-feet, paying particular attention to the lower rear ones (these are usually the ones that are loose.) If you are inclined to put LocTite on them, I'd suggest you replace the screws as well (SAE Grade 5) and use LocTite #272 or nothing - no other grade is formulated to handle the heat. If you replace the screws, be sure to retain and reuse the little "bowl-shaped" washers under the screw heads.

mfpatterson

I found three relays that have all of the same numbers (the top schematic) but the lower right number which shows 30 not 30/50. Advance Auto #R6812, Autozone 19273 and NAPA MPEAR201SB. Any idea if these will work? The other relays I see on line have more numbers slightly different than the numbers on top of the OEM relay.

BTW I ran the test on the fan. When I jump the connector the relay clicks but no fan. When I run juice directly to the fan from the battery it runs fine.

5-90

Sounds like a wiring fault between the relay and the fan, then. Either that, or the relay contacts are burned.

Check thusly: take a short (6" or so) section of 10AWG or 12AWG wire, and put 1/4" male spade lugs on each end. Insert the lugs into the slots on the relay socket that correspond with Pin 30 (power feed) and Pin 87 (power to device) and see if the fan comes on. If it does, replace the relay. If it does not, check for a wiring fault.

The typical DIN relay is spec'd for 30A, although I've seen 30/40A (30A NC/40A NO) and 30/50A (30A NC/50A NO) as well. This refers to both the conductivity/"ampacity" of the relay and the "make/break" current ratings, with the "NC" circuit being pin 30 to pin 87a, and the "NO" circuit being pin 30 to pin 87.

(NC = Normally Closed; NO = Normally Open.)

I'm also looking at a genuine Bosch DIN relay here on my desk (told you I use them all over!) that is rated 20/30A - 20A NC/30A NO. Since these relays are often used as simple "on-off" devices, that's not a problem. And, every draw they're used for in the XJ is under 20A anyhow (often, they're used to reduce the load on a solid-state electronic driver in the ECU, or to take a load off of a mechanical switch somewhere.)

mfpatterson

Thanks again! Do I need to jump the thermo switch when I do this test or leave it plugged in? I'd imagine I can find the Pin 30 with the test light and then do some trial and error to find the Pin 87 power to device, or is ther an easier way?

The truck is going to my 17 year old some once he gets his license. I took it off the road 10 years ago when our daughther was born and after my wife finally threatened to give it away I put it all back together, it runs well so far.

I really apprecaite your help!

Marc

P.S. My other project that is still not complete is my 69 Charger that I had since 1977. The powertrain is solid but it needs some body work and paint.

je4reyk

hi sounds like a bad relay in the mix,the bad one just happend to end up in the feul pump relay spot.that maybe why it whould crank up then stall.On start up the feul pump relay is bypassed.

mfpatterson

Thanks! Do you know what the 4 relay locations are for near the coil?

DalePrice

wow..it must be a time when 1987's are resurrected! I have a 87 wagonner with a 4.0L I ordered in 1986 when they were first available. I over-heated the heck out of it in 1996 when it had 185,000. I went ahead and put a new engine in it at that point, and a new radiator (at the suggestion of the mechanic putting in the new engine). ANyway..it would always start to overeheat when just sitting in traffic, but was fine when moving down the road.....I parked it in 2002 with only 4000 miles on new motor.....anyway, sorry to be so wordy..., but we just moved this past week from the city out to our ranch of 1150 acres south of abilene, texas...and I was just about to call the donate a car folks, then started thinking about what might have been the problem with the overheating, and how nice of a ranch jeep this vehicle would make....a new fuel tank, flush the lines, clean the injectors, change the oil and a new battery, and she was running again..still overheating....noticed the electric fan did not run...ran 12v directly to it....fan ran great....googled 1987 4.0L cooling fan relay and Viola..a thread that had JUST what I needed! I changed out the charging relay with the fan relay...fan came right on....but no charging! Voila, changed out all the rleays, and I have a COOL RUNNING JEEP! Thank you SO much for the help 5-90!

Best Regards,
Dale Price

DalePrice

I am brand new to this, but through trial and error, I can tell you on my 1987 4.0L, the one closest to the front is something to do with the battery charging system, as the volatage was well below 13 when I had a known bad relay ion that slot...the next one towards the rear (2nd from the front)...when it had a known bad relay in it, the engine would not start, although it would crank...I hope that helps some!

Dale

5-90

Doesn't matter. You're simulating the relay being energised by using the jumper lead, so you're good.

mfpatterson

No luck...I replaced all the relays and the fan does not come on. I will now check the wiring to the fan. One other question. In addition to the temp sensor in the head that connects to the temp gauge and the thermo switch I also have a coolant temperature sensor on the block near the anti-knock sensor. I can dissconnect that temp sensor and the car starts, any idea what that one is for? Is it related to the cooling fan too?

mfpatterson

Thanks...glad to hear that this info was helpful to you too!

5-90

Your RENIX has three coolant sensors - the one at the rear of the cylinder head (drives the IP gage/lamp,) the one you're referring to on the driver's side of the engine block (reports to the ECU,) and one in the driver's side radiator tank (Thermal Fan Switch - turns the E-fan on and off.)

The relay for the fan is on the driver's side fender liner, 6" or so back from the crossmember (as I recall. May be a bit farther.) It's the same style DIN relay as the rest.