You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!
New to the forum and have a question that has us stumped.
89 with 200k. Car sat for the last 2 years after the owner died. Cosmetically this car is in pretty good condition, except for some, ok all..the seals and the fact that we cant seem to solve an electrical gremlin.
The fuse panel after much cleaning up of the previous owners disregard to proper wiring of accessories and oxidation of some fuses has left us with three dead circuits. LPS and FP circuits and the heated mirror circuit
I have checked behind the fuse box with a test light on a good ground with the ignition turned on and these have no power to the left side. All wires seem to be good.
Any one have any ideas. We know that its a fuel problem causing a no start issue. We are currently in the process of removing the fuel sending unit to manually check the pump which we suspect of being bad also. Is our ECM module fried, or are there other things that may affect those circuits? When we jump the FP circuit from a good circuit we hear a relay on the firewall right behing the battery clicking. Is this the fuel pump relay?
Any trouble shooting help is appreciated.
So far we have changed plugs, wires, cap and rotor and fuel filter. added fresh fuel with some dry gas and stabilizer, change the oil and filter and stripped off every piece of weather stripping except the B pillar.
Wow - an FSM (with the electrical supplement because there were changes) for what your trying to rehab would come in handy. All of the dead fuses get power from the battery via fusible links which are behind the battery. The fuel pump isn't going to run if it doesn't have power, so dig in and repair whatever links are open. You might also drop the steering column and check for power on both sides of the ignition switch with the key in run, start and accessory. If the voltage isn't the same on the input and the output, try cleaning up the contacts in the switch or replace it too OR if the input is less than battery, you'll need to separate the big harness connector behind the battery and clean it up as well. I might add that it's unusual for a the fuse panel to show corrision unless the car was flooded - either from being under water or the rotten seals you've found let in alot of rainwater. If you have corrosion there, I'd consider a new harness, though they're probably impossible to come by. 200k on an '89 isn't exactly a garage queen so I'm sure there will be a bit more to figure out and until you've got everything getting power, there's no way to tell if the ECM works (but if it's got corrosion on the fuse panel, you might as well take a good look at the ECM connections).
I do not have a Factory one but I do have an aftermarket one.. The one that shows the wrong fuse panel for the 89.. lol... Took us awhile to figure that snafu out.... A better electrical wiring diagram would be better for the 88-90 model years as published in my book. The early years and later years are great... why they decided to use what they did for those years......
Fusable links... Where am I looking for these on an 89? Do I need to pull the battery to access them. So far the only thing I can access around the battery are two relays.. one of which appears to be related to the FP circuit as it clicks when that circuit is activated via jumper.
Oh what I would pay for an OBDII right now on this car.... lol.
If the fusable links are all good.. What other electrical devices are between the battery and the fuse panel. Is the ECM pre fuse panel..?
The Relays directly behind the Battery are MAF and MAF Burnoff. The FP Relay is to right of those (looking forward), towards the Distributor. The Fusible Links carry battery power from the Distribution Block - behind the battery - through the Big Connector just above it - through the Firewall above the brake pedal, and onto the ignition switch (for ignition powered devices) or directly to the Fuse Panel for those circuits which are hot at all times. You should be able to see the links, but removing the battery helps if you need to work on them. To do that, you need to remove the left fender. Note: The a/c fusible link - if you need to troubleshoot it - is from the Starter Motor and not behind the battery.
There were multiple harness changes for the '89 as GM cleared up some known trouble areas and added ZR1 wiring - which never made it into '89 Production. Those changes are reflected in the Electrical Supplement and the Manual Schematics are (basically) for the '88. The ZR1 wiring is only identified in the Foldout Body Schematics at the rear of the Manual. It's unimportant until you start monkeying with the Fuel Pump Wiring (connector at the tank) - at which point, you will find a wire in the harness that goes nowhere. Simply ignore it. My best guess is that the aftermarket simply copied the inaccuracies reflected in the original printing. The '90 is yet another story with the ECM moved from the interior to the engine compartment, a CCM, a different dash and engine management strategy and a host of other changes. Whatever you have sounds like good kindling for the fireplace.
Thanks for the info. I will start at those fusable links and hopefully find my problem there. If not I will have to get into the ignition wiring and test those ignition and accessory leads. They all appear good, but who knows..
Well.... sigh.... we pulled the battery and checked all 8 links that run from the junction block and one that came out of the harness and went to a connector. All had continuity and all had 12 volts passing thru them. We had the battery out and a portable battery jumper connected to the leads. We tested Continuity from the junction block to a point past the black cylindrical "thingy". Never having dealt with these fusable links I'm guessing that the "link" is the wire from the junction block to the black part. One of these wires had a pretty sad jacket around it, but they all tested fine.
I believe that I located the FP relay. Not quite sure what I was looking for, but it was clicking each time power was connected to the system. Also clicking were the MAF burnoff relays right behind the battery so I know that link is good.
I mistakenly labeled the fuse panel circuits that are dead in my earlier post.. They are the FP bottom right, and the INST, not LPS.
I need to track down a good and correct wiring diagram. One that I can read without an electrical engineering degree. That is my task today.
I really need to find one that has the pin diagram for the ECM module so I can test that for bad circuits.
UPDATE. I have located three ECM pin diagrams from Autozones online site. I've narrowed it down to the 1989, and 1990 as possible matches.. Hopefully this will give me some insight next time I am in the fetal position under the passenger dash.
YA YA.. Factory repair manual.. working on that too... just trying to cheap it right now since I'm hoping this will be an easy fix...
Gaskets are on the way so I have some troubleshooting time. Pump is being pulled from the tank today for a direct test.
I am open to any ideas or suggestions as to how to proceed from here. Otherwise I'm going to just keep plugging away shadetree fashion. Right now relays and ignition are my next course of action. Something tells me no to the ignition because other items on those circuits have feed to the fuse panel.
Good news. After much to do about nothing, everything works as it should. Power at the fuel pump for a second or two, then power while cranking. All circuits are alive after some cleaning and a lot of new fuses. Easier to replace than clean each one.
So after tearing out the sender and ordering a china special pump for $30 shipped we should hear this run shortly. Went cheap on the pump for the pump may outlive this vehicle if the MRS. has her way.
$2500 for the car and a hair less than $500 in parts and I think we have a running 89 vette in fairly decent shape. Not to shabby for the start of a financial black hole...
Well, not so good in the starting dept. Fuel pressure with the new pump is good. All circuits working. Problem now is no fuel injector fire. Three injector harness wires pulled on the pass side and one on the driver side with no fire. Tested with a test light while cranking and jumping between the two contacts on each injector harness. (yes...testing the harness and not the injector) I figured that 4 out of 8 is a pretty good bet that both injector circuits are dead. Plenty of power at the fuse panel for the two inj. and ECM/ECU fuses
Here's the wierdest thing. Twice when a spark plug wire was removed on the driver side and a spare spark plug inserted and grounded on either the AC compressor or the alt the engine acted as if it were going to fire. There was combustion for a quick second. Then nothing. This has happened twice, and both times while checking for spark.
Additionally there is no check engine light on the dash showing something else is wrong with those fuel injection circuits. Our two thoughts are bad ground, or bad ECU. This vehicle did run, although poorly before we started the maintenance...spark plugs, wires, rotor etc.
If it is a ground, how many are there on this vehicle and where? I know there's one that the battery neg lead goes to, but where else might I look for others? Also, if it were to be a bad ECU what would I be looking for in terms of testing. I have the wiring diagram, I just need to know what to test for at the ECU.
Any help would be appreciated.
Additionally we did remove what appeared to be an old cellphone unit in the rear of the vehicle. We also know that lojack had been installed in this vehicle. Three wires had been removed from the fuse panel. An orange, red and black ground. Any possiblity that this Lojack unit could be hidden and causing this issue, or would the security module under the climate control unit have the ability to cut just the fuel injection circuit?
With the key on, there should be 12V on the black wire at each injector connector. The ECM applies ground to 'fire' the injector. If no 12V, it's INJ1 or INJ2, or ignition switch . but you say you have 12V at the fuses.
No Service Engine Soon light with key on, not running also indicates a problem. ECM/IGN fuse, or IGN switch. You must fix this (no SES light) first. Then:
Seems like you're not getting ignition refrence pulses. These are required to fire the injectors. If you have spark, try this:
Turn key on. Fuel pump will run 2 seconds and shutoff. Crank for about one second. Leave key in 'on'. Is fuel pump running for 2 seconds and then shuts off? If it is NOT running, there are no ignition reference pulses. Probably the pick-up coil in the distributor, and maybe the module. But probably not the module.
We know the new fuel pump is providing the 1-2 second pre crank pressure build up cycle. Plenty of fuel pressure in the rail. We know there is spark. There is no power to either wire on any of the injector harnesses we tested with the ignition on. No pulsing either when cranking and running a test light between the two wires.
When you mention the pick up coil.. is that the coil that sits atop the cap? If that was bad, would we still get spark? Module = ECM? or something different?
Well, we finally heard the beast roar to life. Not sure if it was from regrounding the main lead from the negative terminal, or disconnecting the ECM and reconnecting the harness wires that did it. It started right up, like it was a new car.
We let it run until we had a bit of an oops moment. Previous owner had run new fuel lines up to the fuel tank sending unit and left the old ones. When we reconnected the lines after the new pump apparently we dropped the current return line and reconnected one of the old ones accidentally.. What occured was a little bit of a cleansing bath for the spare tire. Little speedy dry and 3-4 gallons of fuel later.... we reconnected the CORRECT return line and we were back to normal.
Little bit of light smoke which went away, idling around 900 to start, settled to around 700. Seemed to rev up to 1500 and smoothed out, but still pretty rough at idle. Not sure if this will work it's way out or if we have other issues like clogged injectors. Tranny seemed to work ok but never took it over 10 mph. Brakes really need some attention. Those are next as we really need those to work. Really needed to step on the pedal to stop. Figure 2 years of sitting outside for the last 2 northeast winters probably did no favors to the backing on the brake pads.
Only issues I can see so far is the Anti-Lock light is lit up, and we don't see the check engine light at any time so we are not sure if it even works or not.
Couple of things that caught my attention. First, the oil pressure was in the 50's upon first starting it. After it warmed up it dropped down into the 20's at idle. Mobil 1 syn in it now. Not sure what caused that high reading initially unless it was a sensor problem. Also, she seemed to really heat up fast. Had a low coolant light on at first so we added maybe half a gallon to the radiator. That went out, but it heated up to the point where the fan kicked on after about 10 minutes of idling. Does that sound normal. Fan kicked on at about 226 and dropped it down to the 210 area before it turned off. Temps were in the high 70's outside.
Any suggestions for actions to help the rough idle. We have quite the additive pack in the gas tank right now including dry gas and lots of injector cleaner. Was thinking of a little seafoam. 216k should have a little something to burn off by now.