'87 Cherokee poor MPG, fan doesn't come on

'87 XJ
4.0
automatic
165K miles

Posting for a friend of mine. He delivers pizzas in his 4.0 xj and the poor mpg's are killing his tip money.

There is a strong smell of unburnt fuel when you stand behind it as it's driving away. The cooling fan doesn't come on at all, under any circumstance. It will kick on when directly connected to the battery though. The jeep does NOT overheat.

- Where can the coolant temp. sensor be found on an '87 4.0?

- Any way to check if it's good?

The main problem is the bad mpgs. He has done a basic tune-up. I suggested the coolant-temp-sensor. Anything else we should look at?

How much per gallon is he getting? Cherokees generally do get pretty bad MPG - in the 16-20 range if you're lucky. It's all relative, compared to an Accord, yeah, the MPG is bad, but for a box shaped 4wd 6 cylinder it's not too bad.

Does the fan come on when the A/C is turned on?

caspergotaz28 said:

'87 XJ
4.0
automatic
165K miles

Posting for a friend of mine. He delivers pizzas in his 4.0 xj and the poor mpg's are killing his tip money.

There is a strong smell of unburnt fuel when you stand behind it as it's driving away. The cooling fan doesn't come on at all, under any circumstance. It will kick on when directly connected to the battery though. The jeep does NOT overheat.

- Where can the coolant temp. sensor be found on an '87 4.0?

- Any way to check if it's good?

The main problem is the bad mpgs. He has done a basic tune-up. I suggested the coolant-temp-sensor. Anything else we should look at?

Click to expand...

Sounds to me like the coolant loop is stuck open....either a sensor or a sender.... so yeah, I think you're on the right track.

As far as removing/testing... I'd suggest swinging by an autozone and picking up a haynes manual.

RyleyF said:

How much per gallon is he getting? ...Does the fan come on when the A/C is turned on?

Click to expand...

he's in the 9-12 mpg range. Fan does NOT come on when A/C is switched on.

9-12 mpg to me doesn't sound too far off IMO, for a delivery vehicle doing a lot of start/stop/idling etc. I only get 14-15 the driving to work. The raw fuel smell should concern you, older Jeeps were known to have fuel leaks around the injectors and o-rings, so check that really close.

The sensor that turns on the fan is in the driver's side radiator tank above the hose connection if it has factory A/C. If you don't have the A/C on, the engine has to get around 220' on the gauge before the electric fan comes on. With A/C on the fan should cycle with the compressor. So if the compressor engages, fan stays off, I would check the relay mounted on the driver's side inner fender, right behind the air cleaner. Mine just needed to have the connector cleaned to get the fan to work.

MJmk said:

...older Jeeps were known to have fuel leaks around the injectors and o-rings, so check that really close.......

Click to expand...

There is some fluid puddling on the lip of the valve cover gasket right around the injectors. He definately has a valve cover leak, but the fluid kinda seems like a mix of gas and oil. There is a strong smell of gas when you open the hood after the engine has been off for a few hours. We'll try to see if the fuel line has pressure after sitting overnight.

What all is involved in replacing injectors? Any special tools needed, what about all those o-rings?

MJmk said:

.....I would check the relay mounted on the driver's side inner fender, right behind the air cleaner. Mine just needed to have the connector cleaned to get the fan to work.

Click to expand...

We saw that relay mounted on the driver's inner fender, didn't know what it was for. We'll try to clean the contacts and replace if necessary.