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Pete
Pete, Buick Technician
Category: Buick
Satisfied Customers: 15590
Experience:  15 years Buick Technician experience and training.
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1994 Buick Roadmaster: wont start..rough..really gets going though

Customer Question

Our 1994 Buick Roadmaster station wagon won't start anymore. It's been starting rough for the past month or so, on and off. It turns over, but it makes just a feeble attempt at ignition, never really gets going though. Some exhaust puffs come out, smell like gas. Has 200k miles. Starter sounds good. Battery is charged. Fuel pump sounds good. Replaced oxygen sensors. Checked spark, looks OK. What in the world? We love this car and don't want it to die on us!
Submitted: 3 years ago.
Category: Buick
Expert:  Pete replied 3 years ago.
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.

Hi.

I just need a little more info to assist better.

When you say it was starting rough how was it starting was it running rough at first when started or a hard time starting?

Have you checked spark on all cylinders?

What condition are the spark plugs in?

Has the fuel pressure been tested?

Let me know so we can continue,Thanks Pete!
Customer: replied 3 years ago.

When I said it was starting rough, that meant that when I turned the key, it turned over fine, started after the a second or two (a little slower than usual) but ran really rough for 10 or 20 seconds (like it was ready to conk out), then settled down into running smooth as normally. This occurred maybe half a dozen times over the past month or so. It did not happen every single time I started it, just once in a while.

 

Have not checked spark on all cyclinders, just one. Spark plugs are fairly new.

 

How do I check the fuel pressure?

Expert:  Pete replied 3 years ago.
Can you tell me if this is a 4.3 liter V8 or a 5.7 liter V8?

Let me know,Thanks Pete!
Customer: replied 3 years ago.

Corvette engine, 5.7L V8

Expert:  Pete replied 3 years ago.
O.k.

On the fuel rail with the fuel injectors under the hood there is a fuel pressure regulator.This component will have a vacuum hose on it and should be located on the drivers side back of the fuel rail.

Remove this vacuum line and then turn the key on(don't try to start the vehicle)observe the fuel pressure regulator and see if any fuel is coming out of it.If there is fuel coming out of the vacuum port then the regulator is faulty and needs replaced.

This regulator can cause hard starts,rough running for the first few seconds after a start and in extreme leak cases it can flood out the engine to where it wont start up like this.

This would be the first step I would take here to see if the fault can be found.

Let me know what you come up with here first then we can continue if needed.

Thanks Pete!
Pete, Buick Technician
Category: Buick
Satisfied Customers: 15590
Experience: 15 years Buick Technician experience and training.
Pete and other Buick Specialists are ready to help you
Customer: replied 3 years ago.

Hi Pete,

 

Back again. On the 94 Roadmaster we talked about a while back, it miraculously started up before we did anything to it. It ran for a week or so, and now it won't start again - same symptoms as before. But we'll deal with that later, because...

 

We have a 96 Buick Roadmaster with only 90,000 miles on it and almost no rust. Love the thing! It's always been reliable, except for today. This morning, it wouldn't let me turn the key. The key goes in but I can't turn it. I tried spare keys, same effect. I tried keys from the 94 Roadmaster, same effect. I tried tilting the steering wheel up and down, same effect. Battery is fine. Vehicle is in Park. What the?

Expert:  Pete replied 3 years ago.
Hi.

From what you have described here this sounds like a mechanical failure with the ignition cylinder.

The cylinder has tumblers inside it that when the correct key is installed it will depress these tumblers in order for the key to turn,these can come out of position and in some cases break to where the key can be installed but the cylinder wont turn.

In some cases it can be the key at fault but since you have tried other keys I don't think this is the case here.You can try spraying a small amount of lube like wd-40 or similar into the cylinder hole and then try it,if it doesn't work then most likely the cylinder will have to be replaced or re-keyed by a locksmith to correct this problem here.

Thanks Pete!
Customer: replied 3 years ago.

Hi again.

 

96 Roadmaster started just fine after my husband thawed out the igntion key area; I must have gotten some water or snow in there during a blizzard last night. Oops.

 

Back to the first car. Did what you suggested - fuel regulator does not leak on the vacuum side. Tried to measure fuel pressure but don't have a fuel pressure gage, so just went by observation: When pressing on that little valve in the pipe on the rail, fuel squirted out a couple inches (assume that's equivalent to 40-some psi) right after turning ignition (and hence fuel pump) on and off. Repeating the experiment but not measuring until a minute or so later, turns out there's just a trickle of fuel coming out of the fuel pipe. Must be a leak somewhere, right?

 

The car is 18 years old and mighty rusty on the bottom. Taking off the gas tank to get at the fuel pump is going to be a can of worms. Can it be something other than the fuel pump, i.e. something that doesn't require removal of the gas tank?

 

If we do have to take down the gas tank, do have any suggestions for how to get the gas out of there first?

Customer: replied 3 years ago.

On second thought, I suppose it really doesn't matter so much if fuel leaks somewhere. Isn't the fuel pump running the whole time the car is running, and the whole time we're trying to start the car, turning over the engine?

 

The fuel pump sounds OK, at least it sounds just like the one in our newer Roadmaster.

 

I wonder if 2-3" of squirting fuel is equivelent to 40-some psi. We could check the pressure down by the fuel filter, i.e. before the regulator. What is that pressure supposed to be?

Customer: replied 3 years ago.

Further update: We borrowed a fuel pressure pressure gauge; fuel pressure is perfect and holds. So it's not that.

 

It does seem like there's no fuel going into the engine, so now we're thinking the fuel injectors don't inject an fuel, or not enough fuel, and we're thinking it's a control issue. How can we test this?

 

What do you think?

Expert:  Pete replied 3 years ago.
I apologize for the delay,

Your fuel pressure with key on and engine off should be 41 to 47 p.s.i.

The pump only runs for the first two seconds the key is switched to the on position then shuts off until the engine is cranked several times in a row or the engine is running.

It does sound like you have spark as you had described above in one of the earlier posts so this shouldn't be the problem.It may be that the injectors anent pulsing fuel into the engine.

To test this the right way you would disconnect an electrical connector from one injector(whichever is easiest to get to)then hook this noid light up to the injector connector and crank the engine over,the noid light should blink rapidly when cranking over the engine,if it doesn't then you have no signal to the injector.I have also seen people use a test light to hook in between the two terminals carefully so the pins don't get bent and then crank over the engine and check for a blinking light.

If you can find out if the injectors are being pulsed(the light blinks or not)then let me know we can continue from there.

Thanks Pete!

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