Maroonz2800

Hi, the sending unit on the engine underneath the manifold has TWO wires. one black, one yellow. I know one of these wires leads back to the dash temp gauge, but where does the other lead? I'm worried it leads to the fans that kick in when the car starts runnin hot. is this so?

project89

iTrader: (1)

black wire goes to ground

the temp sensor for the fan is screwed into the cyl head and has a single green wire with white strip

the easiest way to test it is to take the wire off the sending unit and ground out the wire with the key on and the fan should come on.

if it dosent u more then likley have a bad fan relay
if it does come on when u ground the wire but dosent come on when hooked to the sending unit when the car gets hot u need a new fan switch

Maroonz2800

Alright thanks a million man

Maverick H1L

iTrader: (8)

Both wires on the manifold temp sensor go to the ECM... Yellow is signal and the black one is a combined ground provided by the ECM.

Temp switch for the fan is in the rear of the pass side head by the lifting eye (gauge sender is behind the A/C compressor in the same position). It is not needed and can be unhooked. This switch is merely a backup for the ECM fan control (you can check this by noting 2 green wires on one terminal of the relay, one is this fan switch and the other is the ECM). To those who say it's needed, my car is an 87 and the 2.8 had one, as I replaced it when the plastic cap on the end broke off. Since the 2.8 was swapped for a 3.1 in 2004, I haven't had one since, and my radiator fan works just fine (especially since I fixed the PO's and another shop's hacking of the wiring), with the green wire for the switch just hanging out of my wire harness and doing nothing (before I just cut it off).

If the fan doesn't come on with the fan switch grounded, check the relay first and then examine the fan wiring itself right down to the motor. And check that the motor isn't locked up. You can also put a wire in the ALDL under the dash as though you were going to pull the trouble codes from the ECM. If the coolant fan does NOT run, you have a problem in the system.

Maroonz2800

Alright, the fan does work, gauge was replaced, so should run without issue

zs&tas

Hello, can someone just sumarise how many coolant sensors we have, where they are and what they are for ? my engine has thrown a coolant sensor code however the temp gauge works fine ??
thanks in advance
Anthony
88 2.8

fan works too ?

Maverick H1L

iTrader: (8)

3 coolant temp units on most cars, some have 4...
Typical CTS is the one in the intake with the yellow/black wires
Temp switch for the cold start (7th) injector is right next to the CTS with the square connector and a purple wire
Auxillary radiator coolant fan temp switch (if equipped) is in the rear of the pass side head by the lifting eye with a green/white wire in a round squeeze-and-pull-to-remove connector similar to the brake warning switch under the master cylinder
Coolant temp gauge sender is in the same position as the fan switch on the driver's side head (front corner because the head is backwards) behind the A/C compressor or above the power steering pump on those not equipped with A/C, has a green wire with a flat white connector

zs&tas

thank you for that, ive found all four, i cant believe it has four !
what would happen if i disconected the cold start coolant sensor ?
would it not use the 7th injector and would it ever get into full warm mode ? never remember if its closed or open loop which is which haha sorry

Maverick H1L

iTrader: (8)

The cold start injection will cease to function if you delete that switch. Which means that you'll have a LOT of trouble starting in cold weather (ECM isn't programmed for extra fuel with cold starts). CSI has no effect on whether the ECM enters closed loop or not as it is turned off long before the engine is warmed up enough to enter closed loop (160*F, about 65*C, IIRC, and the CSI turns off at about 100*F).

zs&tas

Thanks for that Mav, really useful info, youve helped me out big time.

fishermandude

iTrader: (1)

Mav..question??? I have only three on my 86 2.8 single fan.... I have no fan switch on the passenger side head. The temp sender behind the a/c has a single green wire....If I understood your post earleir..The fan should kick on if this wire is grounded. For my situation the fan still does not kick in. when jumping the ALDL there is still no fan...Engine running a/c switch un plugged a/c on no fan...

I pulled the ecm and grounded the D2 pin and had fan....the relay on the driverside with a red, tan/wh, gr/w, bl/r...when grounding the gr/w i have fan...

I feel that I am so close to whop this its whoopping me.... any advice where to start again

Maverick H1L

iTrader: (8)

Grounding the unit in the driver's side head ONLY turns on the dash light or pegs the gauge. That's all that unit is for, the driver for that gauge or light. There should be a switch in the passenger's side head for the 86. It may be unplugged, but I'm sure the unit is there or coolant would be spewing out of the hole like no tomorrow (it's not plugged on the older V6 cars). Unless someone who owned the car before you plugged it after removing the switch.

Sounds to me like you have an ECM problem if grounding the green wire from the relay at both the relay AND the ECM turns the fan on (fan works, obviously). The ECM should turn the fan on with the ALDL set up for diagnostic mode (wire between the top right terminal and terminal to the left of it). Since you've said that it doesn't, it sounds like your fan driver is damaged.

fishermandude

iTrader: (1)

I also am begining to believe it is a ECM issue...I did a voltage check on the ALDL using a bolt on the driver strut mounting bolt for a ground..PIN A .05 volts, PIN B 5.00 volts...I am not sure if this means anything just thought I would add the info....If the previous owner did a hack job when installing a after market radio could that possibly be causing some of my issues? Also, I pulled the harness from its protective shielding and could not see where a pigtail would have been hacked. Seems unlikely but not impossible.

I could run a new pigtail for the fan switch but have no clue where to begin connecting the leads.

Maverick H1L

iTrader: (8)

There's supposed to be voltage on pin B of the ALDL... Putting that to ground is how the ECM knows to enter diagnostic mode. The pigtail for the fan switch starts at the switch and ends at the relay.

If the ECM is getting ignition power, the dash harness is fine. 80% of the ECM wiring comes in through the pass-through behind the kick panel, including the fan and A/C signals. Go to a yard or search eBay or somewhere and get a spare ECM. Best case, it fixes your problem. Worst case, you have a spare in case the one that's there now dies.

Only part of the fan harness left, that engages the relay, is the ECM, as you've tested that the relay has power to both the coil and the switch by grounding the green ECM wire. You've grounded the wire at the ECM connector and the fan worked, but the fan will not turn on when hot or when the ECM is in diagnostic mode, which points to the driver module in the ECM as being fried.

fishermandude

iTrader: (1)

Just purchased a ECM on Ebay....1227302...should be here on Friday...For a quick refernce only since there is no fan switch the pass head..what is the best setup to run slightly cooler than factory..meaning the thermostat and a new switch that is missing... I have seen a couple of other post but not sure where. I can easily tear back into the harness and splice in using a OHM setting with a voltmeter.

Maverick H1L

iTrader: (8)

Well, if you don't have the switch now, there's probably a plug or something in the hole. If it's plugged, you'll need to fight it out. I'll dig out my old head and try to find out what the best way to get that SOB out is. I don't care if I ruin the head as it's getting junked anyways (going hybrid ), so it's better I do it than anyone else. And I have the whole day tomorrow to kill .

Unless you want to put an aux switch in the radiator. Either way, along with the cooler thermostat (no lower than 180 or you may have problems with entering closed loop operation for better economy), the engine will run cooler without having to reprogram the ECM.

fishermandude

iTrader: (1)

yep it has a plug in it.. not sure how long its been in there so i am not looking forward to it.... any suggestions for the fan switch temp range.. i also looking for the thermostat range... i have seen lots of post for the 8's but having difficulty finding for the single fan 6's. I know there is stuff out there but can't seem to find it again...from what I gather a good start is a 180 stat and a 190 switch..i would like to run slightly cooler than stock but would like to keep some performance... no emmission's to worry about here florida.


EDIT: 86' 2.8 MFPI LB8

Maverick H1L

iTrader: (8)

Blasted PC is being slow again... Read my post above (which I edited just before you posted) and figure your temps right.

fishermandude

iTrader: (1)

MAV....Hope the day off went smooth....How did it go pulling the plug out of the old head... I am sure I will have my hands full.... firewall and such..doesnt look like much but I have no clue how long the darn thing has been there... Picking up the stat and switch today...ecm should be here soon..

Maverick H1L

iTrader: (8)

Didn't get to that yesterday... I knew there was something I forgot to do . I got busy cleaning up my engine block in preparation for the new main bearings I've been waiting 2 months for , and promptly forgot about digging out the pass side head and the dizzy someone else wants. I have to work for most of the light today (no light in the garage right now ), so it'll have to wait for tomorrow.