Hard starting lately

Lately my jeep has becoming hard to start. The weather doesnt seem to make a difference. Its hard to start in the cold and hot. It does however run fine once started. It just takes an unsual amount of time to start the engine. Ive had the battery checked aswell as the starter and they are fine. The sparkplugs are fine aswell. Anyone else have any thoughts as to what might be wrong with my jeep? It also seems to be using up more gas than it used to. Other than those 2 symptoms the jeep runs fine, and the engine is a brand new engine the PO owner swapped in. Any help would be appreciated.

BTW my jeep is a 1990 Laredo renix 4.0 automatic.

more description needed on how she starts.

FYI "jeeps always seem to use more fuel than normal !"

First thing, I would buy some fuel injector cleaner.

Next, I would try to check all fuel related hardware.

check fuel pressure on start up.
might be clogged fuel filter.
might be fuel pump issues.
might be (stretching here) clogged catalytic converter.


When starting my jeep, I always turn key to "on" for a few seconds before cranking it to to "start." She starts right up. Otherwise engine turns over a few times before firing up.

Well when i say using more gas than normal, I mean Im getting like 9 miles to the gallon when I used to get 16ish in the very same jeep. I already cleaned out the injectors. It also smells a bit rich when I drive it. It seems like its dumping more fuel into the engine then it should be.

Ok, little Renix factoid:

The Renix XJs have to "spin up" before they will start. Until the engine is cranking at 300 RPM or higher the crank sensor (CPS/CKP) can't generate a strong enough signal for the ECU to have sufficient data to send the signal to the ICM to fire the spark.

So, the sooner the engine hits 300 RPM the sooner it will fire up. You need a good strong battery, a good starter, and really good cables to get it cranking fast.

Another problem is if the fuel system is draining back. All fuel systems will slowly lose pressure, but if the fuel drains away the problem is magnified. Now, to see if this is part of your problem is quite simple. Turn the key to ON, wait a couple seconds for the fuel pump prime, key OFF, then repeat two more times, then START. If the engine starts faster then at least part of your issue is fuel drain back. You can install an inline check valve back between the fuel filter and the tank. eBay seller jbass195 sells them 3/8" fuel check valve for $16 + s/h $2. Also, if the fuel pressure regulator is bad it could be allowing fuel to drain back.

Its def not a fuel problem. I tried the key trick, also when I try to start the jeep, I can smell the gas. I think its actually to the point where Im flooding the engine. If I press the gas and start it, itll start fine. The jeep also runs rich and you can smell gas while driving it. I checked the spark plugs, and they are starting to foul. Any ideas would be appreciated.

Bad MAP, bad MAT, bad CTS, bad o2, bad FPR, exhaust leak upstream of the o2 sensor.

Testing Renix sensors: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

It is multimeter time.