1989 Trooper with 2.8 not getting fuel

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1989 Trooper with 2.8 not getting fuel

Postby MongooseJake » Tue Apr 13, 2021 9:32 pm

I've glanced over the forums a number of times looking for this specific issue and searched it, but must've missed it...

My issue is that my '89 Trooper with the 2.8 v6 is not getting fuel at crank. I've checked a number of things, but could really use assistance.

Backstory first: Trooper was running well enough before hand. A small hesitation here or there, but nothing big. Started strong, ran well overall outside of a slightly high idle. One day I drove to a jobsite and parked it, moved again around the lot with zero issues, and then went to move again 10 minutes later and zilch. Went from easy start to just nothing.

-Checked fuel pump. Good flow.
-Checked fuel filter. Good flow (was recently replaced and still good)
-Checked spark. Good (will startup with starter fluid or fuel poured into TBI)
-Tested fuel injectors with jumper wires. Good.
-Replaced fuel injector connectors
-Replaced fuel pressure regulator.

Still not getting the fuel injectors to actually shoot fuel into the TBI at crank. Everything seems fine otherwise, but I'm not a seasoned mechanic. Will happily try suggestions! Thanks in advance!
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Re: 1989 Trooper with 2.8 not getting fuel

Postby Oro » Wed Apr 14, 2021 2:05 am

Hello and welcome.

I do not know your vehicle specifically. Maybe someone who does can come along soon with a "BTDT." In the mean time, I'd add two things:

a) I had this issue with a more modern car. Reason turned out to be a disconnected airbag. Computer cut off the injectors because of that. I know you don't have airbags, but maybe think about a safety related reason that might happen.

b) This is a crude flow-chart, but I have never failed to get a non-running car or motorcycle running again by following it. Including my trooper once a long time ago. It's worth book-marking:

https://www.ifitjams.com/starting.htm
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Re: 1989 Trooper with 2.8 not getting fuel

Postby Ed Mc. » Wed Apr 14, 2021 11:41 pm

It's possible the ECM went South, or some bad connections/wiring to the ECM.

The injectors see 12VDC on a common side all the time. The ECM grounds the injectors to energize them. So if you've lost the connection between the Neg side of the injectors to the ECM, that would cause a problem. Although it seems unlikely that it'd be running and then minutes later these wires would fail.

There's a black wire with red stripe hanging out under the fuel pump relays in the fuse box; if you connect this wire to the Pos terminal of the battery, the fuel pump will run constantly, bypassing all the relays and ECM control. If the engine will run then, you've maybe got an issue with one of the fuel pump relays.

If it still won't run, and you can confirm you're getting fuel pressure at the TBI unit, I'd be taking a hard look at the ECM circuits that fire the injectors. Check the continuity between the injectors and pins D14 & D16 on the ECM.

I've attached a few diagrams that might help.

If the ECM is bad, check your local Pick-n-pull or whatever you have. Also check http://www.car-part.com A 3.1 Rodeo or Pickup ECM will probably run the 2.8, as well. Early 90's GM minivans with iron-head 3.1 that had a throttle body like your 2.8, are also good candidates for a used ECM. Check eBay, there's usually something there as well.

https://www.ebay.com/sch/Engine-Compute ... 5&_fosrp=1

https://www.ebay.com/itm/12280622-GM-EC ... Sw4vFgWLzh

HTH & Welcome to the Planet!............ed

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Re: 1989 Trooper with 2.8 not getting fuel

Postby Enemigo » Thu Apr 15, 2021 12:24 am

Oro wrote:
b) This is a crude flow-chart, but I have never failed to get a non-running car or motorcycle running again by following it. Including my trooper once a long time ago. It's worth book-marking:

https://www.ifitjams.com/starting.htm



Thanks!
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