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General Forums => The Mess Hall => Topic started by: Schris1 on June 06, 2007, 10:52:02 PM
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1986 2.5L throttle body injection Jeep Cherokee. The Jeep has had trouble starting in the mornings. Now it doesn't want to start at all. I have to crank it multiple times before it will even consider starting. I found that fuel isn't being sprayed during cranking The butterfly in the throttle body is completely dry. If I spray some carb cleaner in the throttle body, it will start right away. Once it's started, it runs fine. It does have trouble starting at other times through out the day. I checked the fuel pressure and it's reading fine (15-17 psi). I am thinking that the injector is bad, but I want to know for sure before I speed the money for it. Any ideas?
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I had the same problem with a GM TBI engine. Turned out that there was a module that regulated injector pulses that was bad. On this motor it was inside the distributor. Don't know where it'll be on your jeep. Makes sense to me though the computer doesn't know that the engine is trying to start so it doesn't fire the injector. Hope this helps. Good luck!
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Sounds like this job calls for a Factory Service Manual. Pays for itself.
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Sounds like this job calls for a Factory Service Manual. Pays for itself.
Any idea where to get one?
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Sounds like this job calls for a Factory Service Manual. Pays for itself.
Any idea where to get one?
An '86 FSM would have to be a reproduction since I'm not sure if they still make them. You can problem get them online at Alldata.com (http://www.alldatadiy.com/). You'll have to pay for the downloads. I'm sure it's cheaper then buying a FSM , too.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=120129376781
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280122776251
This is a Chiltons on CD: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280121448072
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You may find what you need here:
http://www.books4cars.com/search.asp?findmake=Jeep&offset=100
If you can't find an FSM, the Hayes and Chiltons manuals are usually good enough and are easy to find at the auto parts stores.
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Prognosis Doctor? ???
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I have access to Alldatapro and from my understanding, it's the ECU that controls the injector. There aren't any electronics in the distributor. I am definiately getting spark to the distributor. There just isn't any fuel coming out until it's running.
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Seems like this is not uncommon on older 2.5l Jeeps if you have spark then check for injector puls while cranking.
If not look at the ecm as long as there is spark the ecm should recognize it and start firing the injectors. I have heard of more than a few of jeeps doing this one thing you can try if it does not start when cold is warm the ecm up with a heat gun or something don't cool it but get it to 100 degrees fharenheid or hot to the touch and see if it will start or when its wharmedup cool the ecm in the fridge and see if it will start
Art
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Like I said before my only experience with this problem was with a GM product. That being said part of the diagnosis included splashing a small amount of fuel into the TB opening, the engine fired and stayed running at 1600rpm and higher, that's how we ruled out a bad injector. Come to find out for start up the engine got a different signal for injector pulse. That's when we stumbled on the pick up inside the distributor. Evidentially the computer didn't control the engine until after start up. I don't know if this is any help to you, but that's my experience in a nut shell.
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Sounds like the computer isn't picking up the correct signal or combo of signals to add the fuel. Check a FSM for diagnosing the camshaft position sensor and crank position sensor.