Update: Hard Starting Issues: Fuel Pump?

[Donne Trav]

After installing a brand new AC Delco Fuel Pump Thursday evening, my '94
cranked right up this AM. Hurray for that! However, I'm not driving it yet because it
it still has a "rough" idle. My weekend project will consist of adding the new AC
Delco Fuel Filter and maybe a Fuel Pressure Regulator. If these don't help the
problem, I'll have to look into doing the "Fuel Injector" tests. The very LAST THING
on my mind is dealing with the all-too-expensive, troublesome, piece 'o s- - - OPTI
SPARK . Ugh! Your thoughts concerning the possible "rough" idle issue. THANK

[Hib Halverson]

It is unlikey a new fuel filter and a new FPR will solve a problem with rough or unstable idle.

The fuel filter replacement is good for other reasons provided it hasn't been replaced in the last 24,000-36,000 miles. I'd only replace the fuel pressure regulator if the FSMs fuel pressure diagnostic information says to do it. The FSM contains information on how to test the fuel system for a faulty FPR and, if you have the proper gauge, the decision on the FPR replacement is easy to make.

The technique of "trial and error" or "throwing parts" at a problem on a chance basis is a waste of time and money.

My suggestion would be to consult the FSM's diagnostic information on rough or unstable idle and work from there.

It is true that the Optispark ignition could be a problem but...there are many other causes for rough idle (leaking injectors, heavily-deposited intake valves, compression problems, O2 sensors, etc) and the only way to solve the problem with minimal cost is by doing proper diagnosis first.

Is the engine running rich at idle? Is it hard to start after a period of operation, ie: you drive for a while, park the car for 10-15 min then come back to find it hard to start and acting like it's flooded?

What is the general condition of the ignition system?
When's the last time O2Ses were replaced?
How bad is the "rough idle"....are we talking a constant misfire? Are we talking an intermittent misfire? Is it always the same cylinder or different cylinders?
How many miles are on the engine?

[John Robinson]

What Hib said is correct. Lets see if I can get this correct there is an old saying from the days before electronic ignitions. Low speed miss electrical (Plugs & Wires) High speed miss valves. Now I have just replaced the wires and plugs on my 93 with 93K on it. The idle is smoothed out and the darn thing scared me the first time I drove it because it lit the back end up with tire smoke and I have never had it do that since I bought it. Oh and the ASR was active.

[Donne Trav]

It is unlikey a new fuel filter and a new FPR will solve a problem with rough or unstable idle.

The fuel filter replacement is good for other reasons provided it hasn't been replaced in the last 24,000-36,000 miles. I'd only replace the fuel pressure regulator if the FSMs fuel pressure diagnostic information says to do it. The FSM contains information on how to test the fuel system for a faulty FPR and, if you have the proper gauge, the decision on the FPR replacement is easy to make.

The technique of "trial and error" or "throwing parts" at a problem on a chance basis is a waste of time and money.

My suggestion would be to consult the FSM's diagnostic information on rough or unstable idle and work from there.

It is true that the Optispark ignition could be a problem but...there are many other causes for rough idle (leaking injectors, heavily-deposited intake valves, compression problems, O2 sensors, etc) and the only way to solve the problem with minimal cost is by doing proper diagnosis first.

Is the engine running rich at idle? Is it hard to start after a period of operation, ie: you drive for a while, park the car for 10-15 min then come back to find it hard to start and acting like it's flooded?

What is the general condition of the ignition system?
When's the last time O2Ses were replaced?
How bad is the "rough idle"....are we talking a constant misfire? Are we talking an intermittent misfire? Is it always the same cylinder or different cylinders?
How many miles are on the engine?

Well, I've added the new AC Delco FUEL PUMP along with a new FUEL FILTER. And it still takes too long to start and has a "not to bad roughness"
in the engine at lower speeds. Literally can't ride in 6th gear because of a
loud "knock" along the "shakes". I had OPTI problems long ago, and this is
what I believe is wrong now. Wish there was an easy way to diagnose the
OPTI. There's 68,000 miles on this "94. Thanks for the response.

[John Robinson]

Have you replaced the plugs and wires? If not it is time because no matter if they are good for 100K when the car is new time has destroyed them. You talk about not being able to run in 6th gear because of vibration. On my 93 the vibration was so bad on the I slab that I thought the differential was going bad or a rear bearing. I drove my tire dealer nuts trying to re-balance the tires also. The end of this story is when I changed the plus and wires the car suddenly repaired all those imagined problems and it runs smooth again not to say anything about the 4 MPG I gained.


The first thing everybody wants to do is blame the opti for a poor running car. If I had all the money spent on replacing opti;s that were not bad I could float the banks a bail out loan

[gmjunkie]

The first thing everybody wants to do is blame the opti for a poor running car. If I had all the money spent on replacing opti;s that were not bad I could float the banks a bail out loan

You got that right John!! If we had the $$$$$$$ spent on Opti's that weren't bad I've seen the last 10 years,Both our Family's would be in the Bahamas soaking up sun shine for the rest of our lives!!!!

[John Robinson]

You got that right John!! If we had the $$$$$$$ spent on Opti's that weren't bad I've seen the last 10 years,Both our Family's would be in the Bahamas soaking up sun shine for the rest of our lives!!!!

Sounds Good Junk. When do we leave? When I changed my plugs and wires earlier this week I forgot to install the small hose to the water pump and all of a sudden I had antifreeze all around me. Guess were all that water was going. Yep the opti got soaked. When I started the car it ran terrible. I found the new coil wire spark was jumping to the block about 1". I went back where I got the wires and asked for a new coil wire because the car was running rough. The first thing the clerk said was You Need a new Opti. I started to recheck what I had done and discovered that when I ran the #1 wire to the opti I had forgotten to put it on the opti. Wouldn'T I have felt stupid if I had rushed into having someone replace the opti when it was not bad.

[formul8]

Have you replaced the plugs and wires? If not it is time because no matter if they are good for 100K when the car is new time has destroyed them.

Not even 100K. I replaced the plugs and wires on my old '96 Z28 at 40K. Half the plugs were missing the "pucks" and one of the wires was already dried and cracking. The car was only 4 years old at the time.

NGK TR55 and MSD 8.5 wires and the thing was HEALTHY after this change!!

[garyg]

I had experienced an idle problem and seeked guidance here in the forum. I replaced the fuel pump relay (cleared that code), replaced the MAF relays (cleared that code) the problem continued, although I was actually suspecting the IAC valve.... but in a reply here by Vader 86 he suggested disconnecting the battery for a few minutes then reconnecting it to reset the ECM.

It worked and the car is running perfectly. Maybe it was magic...

[Donne Trav]

I had experienced an idle problem and seeked guidance here in the forum. I replaced the fuel pump relay (cleared that code), replaced the MAF relays (cleared that code) the problem continued, although I was actually suspecting the IAC valve.... but in a reply here by Vader 86 he suggested disconnecting the battery for a few minutes then reconnecting it to reset the ECM.

It worked and the car is running perfectly. Maybe it was magic...

THANKS for your reply. After replacing fuel pump, fuel filter and fuel pressure relay, it started right up as it should. LOVEd IT! But it still had an uneven, "hard-like" spot in the idle. Too much vibration on acceleration, etc. I then noticed one of my PLUG WIRES had embedded itself onto that "tinny" part of the exhaust manifold. When I pulled it away, I could see the "arcing" to the manifold (Thank goodness for overcast skies). I then pulled the wires far enough away as to rid the "arc" — car has never run better. THANKS ALL