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Unread 07-12-2013, 06:16 AM   #1
crackedcornish
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are TBI injectors rebuildable?

my '88 has been going through a ground up rebuild for a couple of years now.
I finally have everything just about put back together now, and went to start it up yesterday with no joy

I'm getting fuel to the throttle body with the injector removed, but no fuel through the injector when it's installed.

when I took the injector out of the throttle body I could see some residual fuel behind the little screen they have, but no fuel is being sprayed into the manifold when I'm cranking the engine

so can these TBI injectors be cleaned/rebuilt, or are they sealed so you can't do anything but remove and replace 'em?

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Unread 07-12-2013, 10:54 AM   #2
Old4X
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You can clean the screen and replace o-rings, that is about it.
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Unread 07-12-2013, 11:04 AM   #3
bgredjeep
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Are you sure you are getting the power to the injector to make it fire? If it was clogged or dirty I would still expect to get something out of it when you try to crank the Jeep.

You could pic up a kit like this to test and make sure you are getting the signal to fire to injector. I used this to find the issue with my Howell install when I wasn't getting a good tack signal so the injectors weren't firing properly.

http://www.amazon.com/Performance-To...+injector+test
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Unread 07-12-2013, 11:16 AM   #4
crackedcornish
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Quote:
Originally Posted by Old4X View Post
You can clean the screen and replace o-rings, that is about it.
thanks, I was afraid that was the answer I was going to get, but I figured it wouldn't hurt to ask...you know, just in case I was missing something obvious about disassembling one
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Unread 07-12-2013, 01:35 PM   #5
LJameson
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Are you sure your wide open throttle switch isn't stuck making the ECM think its in WOT? If it is, then it shuts off fuel going to the engine incase its flooded.

Edit: Do you have spark? Have you tried putting some fuel into the intake to see of it starts? It could also be a crank sensor problem if you don't have spark and fuel.
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Unread 07-12-2013, 01:38 PM   #6
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Quote:
Originally Posted by LJameson
Are you sure your wide open throttle switch isn't stuck making the ECM think its in WOT? If it is, then it shuts off fuel going to the engine incase its flooded.
This would be the same system that allows you to start the Jeep with leaky injectors right?
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Unread 07-12-2013, 03:34 PM   #7
crackedcornish
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Quote:
Originally Posted by LJameson View Post
Are you sure your wide open throttle switch isn't stuck making the ECM think its in WOT? If it is, then it shuts off fuel going to the engine incase its flooded.

Edit: Do you have spark? Have you tried putting some fuel into the intake to see of it starts? It could also be a crank sensor problem if you don't have spark and fuel.
yes, I have spark...I'll have to check the switch for throttle position

I put some quick start into the throttle body and got a couple sounds (sounded like some light backfire from the tailpipe...you know...put,put) from it trying to fire, but it didn't try to run on the quick start
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Unread 07-12-2013, 06:03 PM   #8
Cherokid
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My '89 shut down on me once and a couple of good raps on the injector 'unstuck' it. Maybe it's gummed up from lack of use. Couldn't hurt... much. I think I priced them back then (less than 6 months ago) and came up with $150-ish for a new one.

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Unread 07-12-2013, 06:08 PM   #9
Old4X
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Fuel pressure good at the TB? The injector is a solenoid operated valve that sits in a pressurized fuel bath. When it receives an electric pulse, the needle is pulled off the seat and pressurized fuel squirts out.

No pulse from the computer, no squirt, AND no fuel pressure, no squirt either.
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Unread 07-12-2013, 09:19 PM   #10
crackedcornish
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it's entirely possible that the injector nozzle is totally gummed up...this motor hasn't been turned over in several years, and there wasn't any type of treatment added to the fuel before it went into storage. The original plan was for the Jeep to be down for a week, but some things in life didn't work out as quick I had hoped it would, so unfortunately, no prep was done for long term storage.

I'm going to try soaking it in fuel injector cleaner and see if that loosens up any garbage that may be inside the injector itself...then I'll give it a couple of good raps for good measure

Old4X,I don't really have anything as far as diagnostic tools go, so really can't give you a definitive number about the fuel pressure. I did get a pretty good amount (I'd guess about 30cc's or more) of fuel squirting through the throttle body (with the injector removed) when the pump primed though.
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Unread 07-30-2013, 06:58 PM   #11
crackedcornish
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had a chance to play with the Jeep today, so I replaced my injector with a rebuilt unit from Python ($35) and I'm still not getting any fuel through it...could any of the sensors being bad keep it from pulsing or is this strictly a case of a bad ECU?

what kind of of voltage should be showing on my injectors wiring if a stick a multimeter on it and crank the motor?
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Unread 07-30-2013, 07:51 PM   #12
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A multimeter is the wrong tool for testing the impulses at the fuel injector. You need to use a noid. It is basically a 12 volt LED that indicates by flashing if the signal is getting through. The pulses are so short, your multimeter won't read them.
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Unread 07-30-2013, 08:02 PM   #13
crackedcornish
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OK, say I had this noid and it flashed what would that tell me...I have two bad injectors?

and if it didn't flash....I have a bad ECU?
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Unread 07-30-2013, 08:49 PM   #14
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I believe you have a Renix FI system. If you have the proper troubleshooting manual they are supposed to be the easiest of all FI systems to service, only needing a multimeter for most of the tests.

Non firing injectors aren't necessarily indicative of a bad ECU. Many faults can take the system off line.

I do not have experience with the Renix system, but several here do and should be able to help you. Change the post title to something like "Need help on 2.5 Renix system" and you are more likely to find the right person. Your title led me to think you had a Howell system.
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Unread 07-31-2013, 01:01 PM   #15
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Is there a relay for those? I am not hip on the renix system either, two of my XJs had it but I didn't have any problem with them.
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