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Discussion Starter #1
Hello everyone,

Looking for some advice on my Roadmaster. Since I got it, it would intermittently not start, start slow when warm, or even shut down when driving.

The problem seemed to have gone away for months, and has recently returned worse than ever.

FYI I did change my fuel pump and coil last year.

Recently, the car would start in the morning, then shut down in my driveway while I was closing the garage door. Then, it would restart, but shut down while driving 6 miles to work. Yesterday it shut down twice on a 6 mile drive.

Thing is, during the day it would start right up, and never miss a beat. The same for going home, starts right up, drive home with no problems.

Then, in the AM, trouble all over again.

I'm wondering if it could be the relay. I can't remember, but I might have even changed that.

Anyway, I really appreciate any advice on this one.

Thanks everyone.
 

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It might be your temperature sender on the front of the intake manifold, by the thermostat housing.
 

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Discussion Starter #3
Thanks Fred, I'll check that.

It's been like a "ghost in the machine".
 

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I have been reworking a couple of wiring harnesses for an engine swap, and one of the common issues is the wiring that goes under the front of the engine. All had some issues, and two of three were really deteriorated. The insulation becomes brittle, and the wires can become exposed. The wiring is for the O2 sensor, alternator, purge solenoid, and power steering pressure switch (maybe a couple more for the wagons). If these wires touch, you could get some strange reactions from the engine, especially the O2 sensor wire. There is about 10 inches of wire that is affected by this. It is not easy to access, usually dirty and greasy, and would require splicing of wires. I have also noticed that the wires do not like to be soldered, so weatherproof butt splices are the way to go. Space them so that they do not overlap, and you can use a reasonable size loom to cover them. To get the proper color wires, you will have to get a large portion of the engine harness, probably from the firewall to the front right side about halfway down.


I an not telling you that this is the issue, but it could be. You may be opening a can of worms trying to fix it on the car. The wiring harnesses are different for the 91s, and different for the sedans vs. wagons. If you need to make this repair, get the wires from another harness that match the colors of the original wires.
 

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Discussion Starter #5
Thanks again Fred for taking the time to give me this detailed response.

One thing, my car has a column theft guard, and one day I smelled electrical burning, and my blinker wouldn't work. It went away, but I guess it's possible I have some short in there as well.

The engine does turn over though, so I'm not sure if anything in the column would produce these symptoms.

I'm working on it this weekend, so hopefully I'll find something.

I really appreciate your help.
 

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Discussion Starter #6
Checked and have no codes.

Just tried it. Started right up. Removed relay and inspected, looks good. Started again, no problem.

It's running in my driveway right now, hasn't stalled. Light rain and humid right now, I don't know if that could make a difference.

I'm going to look at the harness where I can in the morning, thanks again.
 

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Discussion Starter #8
I'm thinking a bad distributor

Thanks.

I disconnected and reconnected the harness this morning. There was a spot in the harness that appears to have been soldered, under electrical tape. Anyway, it started right up. I drove it several times today a short distance. No stalling, started right up every time.

It's tough to diagnose an intermittent fault. I'm going to drive it and hope for the best.

The distributor could be the problem though. If it is, I guess I'll only know if it completely fails.

Thanks for the advice everyone.
 

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The distributor is usually not the problem. They are simple, and will even work with a cracked magnet. The only issue you might have with the distributor is that it might cause some minor timing fluctuations, if the bearings are worn, and the shaft wobbles. Intermittent issues are usually either poor (intermittent) grounds, or wiring shorts that occasionally make contact. These do not always throw a code. The most notorious ground issue is probably the one at the thermostat housing. The most suspect part of the harness for shorts is the part under the front of the engine.


Vacuum leaks will not show up as a code, and the lines are getting brittle from age.


Most of the sensors can be checked for function. The engine temp sensor on the intake is critical, and can cause the engine to shut down. The EGR valve can be checked for operation, as well as the solenoid that operates it.


During open loop operation the computer uses internal references for the sensor inputs. The only time the sensors are checked by the computer is during closed loop operation, so if it does not start cold, the issue is probably not a sensor.
 

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Discussion Starter #10
hey everyone

I have some additional info that I figured out, so I'm putting it up here with the hope that someone will have an idea about what the problem might be.

As stated in my earlier posts, the car started fine the other day. I started it several times and it immediately started every time.

Thing is, I never let the engine get up to operating temp. I just started it up and then immediately shut it down. Then in the evening, I started the car without issue, and let it get up to normal temp just driving it around my area.

Then, I drove it back into the garage, and shut it down. When I got up the next morning, the car would not start. Then, when I got home from work, I tried it again. Of course it started right up.

I'll add that when it does run, it runs fine, although when the car is warm it will stall often when restarting, especially if it's hot outside.

Anyway, last night I tried to replicate the results from the other day. I started the car several times over an hour or so, each time with no problem, started right up, every time. Then, as with the other evening, I took the car for a local drive to bring it up to operating temp, then drove it home into the garage and shut it down.
So this morning, just like the other morning, it wouldn't start, even after several tries.

I tried some starter fluid in the intake today, and it DID kick over, but died quickly. So I'm thinking it's fuel related, but not necessarily the fuel pump.

I did change the fuel pump a couple years ago. Any thoughts on this one? I don't want to change a good fuel pump, but I'm also running out of ideas.

Thanks everyone, as always.
 

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Intermittent issues can be a pain. When it's in the no start state, I would check for 2 things (assuming it's cranking over), fuel and spark. Listen to see if you hear the pump prime or use the prime override wire to see if the pump will run continuously and try to check the pressure at the rail too.

Just cause the pump was replaced, doesn't mean the wiring/connectors in the tank aren't causing the intermittent issue. I know this one first hand. If that looks good, do some tests to see if you are generating a spark at he plugs. The sticky has a good diag thread that will walk you thru some systematic steps to isolate the problem. Good luck.
 

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Discussion Starter #12
Intermittent issues can be a pain. When it's in the no start state, I would check for 2 things (assuming it's cranking over), fuel and spark. Listen to see if you hear the pump prime or use the prime override wire to see if the pump will run continuously and try to check the pressure at the rail too.



Just cause the pump was replaced, doesn't mean the wiring/connectors in the tank aren't causing the intermittent issue. I know this one first hand. If that looks good, do some tests to see if you are generating a spark at he plugs. The sticky has a good diag thread that will walk you thru some systematic steps to isolate the problem. Good luck.

Thanks 4DoorSS,

Just because I don't want it to be in the fuel tank doesn't mean it isn't.

I am mystified by the fact that it only occurred after bring the engine to operating temp and letting it sit overnight after that.

It would not start this morning even with several tries.

I just started it now. Fired right up. I said to wife sitting in the garage, "I'll bet it starts right away". Sure enough, it did.

It doesn't seem that an intermittent electrical fault would be so predictable. It would also seem that if it was the pump, and somehow related to the pump getting hot or whatever, that sitting all night from last night would have let it cool enough to fire up this morning.

Anyway, I'll check the stickies as you suggested. Thanks for the advice.
 

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Discussion Starter #13
Question about fuel pump

I'm getting ready to replace the fuel pump. I don't want to end up with another POS, I changed it out two years ago with a locally purchased part.

To be fair, I don't know if the problem is the pump or a connection in the in tank assembly. For this reason, I'm planning to replace the whole mess.

This is the part I'm looking at getting:

https://www.rockauto.com/en/moreinfo.php?pk=1322974&cc=1022094&jsn=438

My question is about the Delphi part, does it have a good reliability history?

Thanks
 

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Can't say on the Delphi part but I have the Spectra unit and so far it's been ok.

But as long as the current unit is fine and not rusted out, I'd probably just save my money and clean up the current unit. Not a whole lot that can go wrong with the sending unit besides the wiring and connections which can be replaced or cleaned up. Racetronix offers new wiring kits to help cleanup and improve the stock unit for a little less money than a new unit.

However, a new sending unit may just give you some piece of mind. This can be worth the cost of a new unit. Just pay close attention to the gauge of the wiring compared to your old SUnit. I didn't like the ground wire on the spectra and made some improvements to it when doing the last FP upgrade.

http://www.impalassforum.com/vBulletin/34-engine-problems-maintenance/1239986-fuel-sending-unit-gm-vs-spectra.html
 

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Discussion Starter #15
Thanks.

The reason I'm thinking about the whole deal is because I replaced the pump only about two years ago.

Right now the car starts every time. I took it for a 12 mile drive today with no issues.

The non start times have been almost always in the morning when the car had been driven the day before, as opposed to started but not warmed up.

That's the reason I suspect the pump itself, as opposed to an electrical fault.

I'm going to wait until the next time it doesn't start and check the voltage at the harness.

I don't want to "throw parts at it", but I can't trust it. Whatever it is, I wish it would just break completely, so at least I could know when I fix it!

Thanks again for the advice.
 

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this issue is not being properly diagnosed. have your fuel pressure gauge ready and VOM . is it spark/fuel ????? your guessing that will cost you lots of time and unnecessary costs.
 

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this issue is not being properly diagnosed. have your fuel pressure gauge ready and VOM . is it spark/fuel ????? your guessing that will cost you lots of time and unnecessary costs.

Thanks j cat,

I tried to start it a little while ago. As expected, after running enough this morning, and then letting it sit all day, it wouldn't start. I tried several times.

This time, afterward, I disconnected the fuel pump harness and put a meter on it while my wife tried to crank it several times.

Each time she turned it over I got 12 volts on the meter.

Then I let it sit again for about 1/2 hour, went out and tried it again, and it started. It started just slightly slower than usual, but once started, it ran fine with no unusual symptoms of any kind.

Since it always starts eventually, I don't know what test I could be making when it always seems to "fix itself".

Of course I know that whatever it is will likely get worse eventually.

So right now the car will start right up. No codes.

I'll add that a few days ago, when it wouldn't start, I sprayed some starter fluid in the intake.

The engine grudgingly fired, then died quickly. I repeated this three times, each time with the same result. Then I tried starting it with no spray, and nothing. It turned over but didn't fire.

I'm not sure, but wouldn't this indicate a fuel problem, as opposed to ignition?

Also, last week when it wouldn't start, I gave the bottom of the fuel tank a hit with a rubber mallet. Again, it fired right up.

One of the other times I put 12 volts to the test lead behind the A/C accumulator, and it still wouldn't start.

I listed carefully for the pump each time, and I don't think I heard it on the times it wouldn't start, but I will admit it's difficult to hear. I do think I hear it when the car does start, but again, it's very faint.

I do hear the relay, every time. I changed that a couple years ago as well.

All that has me looking at the pump, but I'll admit I'm confused, because once it starts, there are no symptoms to diagnose.

I know that the TBI has no schrader valve, so I guess I'd need some special fittings to test the pressure. I'll look into that.

Thanks for your advice.
 

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Maybe try a voltage drop test. Might be an intermittent ground issue.
Any drop when you put a meter in the - circuit at the battery?
 

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I thought that the 92 buick had the TBI . as well as the non opti system. I know a guy that has one and he purchased this 92 because it had no opti....

install a fuel measuring port and hook up a pressure gauge. drive around with it connected. with the vehicle running measure the volts at the rear pump connector . under load if you have a bad feed voltage it will show if its not under load the wiring/connector issues if any will not show any voltage drop.
wiring and grounds back in the rear sure can be the problem.
fuel pressures being shown erratic and a voltage test will narrow it down to pump or wiring.

possible that the TBI is leaking down when off .. possible the TBI is with bad wiring. carb cleaner will damage these coils .. only use TB cleaner .
with what you say seems like fuel problem.
a bad distributor would get the CEL to act up.. no CEL more toward a fuel delivery issue.
 

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This time, afterward, I disconnected the fuel pump harness and put a meter on it while my wife tried to crank it several times.

Each time she turned it over I got 12 volts on the meter.

this is normal and you should just see it for 2 seconds or if you use the prime wire, constant. Did you meter across both the Gray and Black wire of the 3 pin connector? Don't ground your meter elsewhere on the car and then just touch the gray wire for 12v. Doing this will not indicate if you have no ground (which comes from the trunk area) to the connector

Then I let it sit again for about 1/2 hour, went out and tried it again, and it started. It started just slightly slower than usual, but once started, it ran fine with no unusual symptoms of any kind.

Of course I know that whatever it is will likely get worse eventually.

YES...it will :frown2:

I'll add that a few days ago, when it wouldn't start, I sprayed some starter fluid in the intake.

The engine grudgingly fired, then died quickly. I repeated this three times, each time with the same result. Then I tried starting it with no spray, and nothing. It turned over but didn't fire.

that cause it have enough from the spray to fire off, then it quickly burnt up. Sounds to me like you have spark.

I'm not sure, but wouldn't this indicate a fuel problem, as opposed to ignition?

to me and based on what I've read....Yes

Also, last week when it wouldn't start, I gave the bottom of the fuel tank a hit with a rubber mallet. Again, it fired right up.

that right there is the classic test that something in the tank is loose. Could be a fuel pump, wiring, connections or all of the above.

One of the other times I put 12 volts to the test lead behind the A/C accumulator, and it still wouldn't start.

another indication that the wiring to the relay is not the culprit.

I listed carefully for the pump each time, and I don't think I heard it on the times it wouldn't start, but I will admit it's difficult to hear. I do think I hear it when the car does start, but again, it's very faint.

use the prime override wire here, lay under the tank with the car keyed on and have someone remove then attach 12 source to the wire and you will hear it going off and on. Some pumps are quieter than others and the amount of fuel in the tank may muffle that sound.

I do hear the relay, every time. I changed that a couple years ago as well.

All that has me looking at the pump, but I'll admit I'm confused, because once it starts, there are no symptoms to diagnose.

yeah, til you hit a bump or the connection decides "I'm not working today just to piss you off".

I know that the TBI has no schrader valve, so I guess I'd need some special fittings to test the pressure. I'll look into that.

didn't know that as most cars have one somewhere to test. Maybe look into some sort of inline tester you can mount near the fuel rail?


Thanks for your advice.
Everything you describe (to me) is pointing to an "intank problem". I've had the same issue and symptoms as you described after a fuel pump change that worked fine for a while. Then at the worst time (500 miles from home) the car quit for good. It was diagnosed as a bad/burnt ground connector in the tank.

I removed some of your post to focus on the symptoms you described and why I think this is in the tank. My responses to each is above in RED. Maybe this will help you but think you need to drop the tank as the voltage to the tank sounds fine. Good luck.
 
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