GMC Suburban

1999 GMC Suburban Engine Won't Start When starting Always

I am afraid I am going to wear out my starter prematurely! Engine used to crank right up, but is becoming harder and harder to start, at any temperature. After finally starting, it may miss sometimes for a few seconds with rich exhaust, then smooths out, runs fine after that. I would suspect fuel starving except for the rich exhaust. Plugs replaced, no help. I need somebody smarter than me to tell me what to try next.

Which engine do you have?

You need to check for spark when the engine will not start.

The PCM (computer) should be scanned to see if any trouble codes exist that will assist in diagnosing the problem. Autozone will scan the trouble codes free of charge.

1999 GMC Suburban Heating / Cooling System Malfunction Happens always Always

My front blower motor is not operating even after I replaced it with a new one, what could cause this? The rear blower works.

If you are getting power to the blower motor, repair your bad ground wire. If you have no power on any speed setting, check the 25a fuse in the dash fuse box, the blower switch, and the blower relay.

1999 GMC Suburban Electrical / Lighting Systems   

I change the pos. side terminal to the top terminal on the battery becuase of corrsion. Now the vehicle turns over but won't start. I cannot hear the fuel pump. What did I fry?

Check the fuel pump relay and fuse.
The ground for the fuel pump is actually the black wire on the thermostat hsg. Chrck that.A temp hot lead can be wired from batt + terminal to fuel pump.

1997 GMC Suburban Electrical / Lighting Systems Malfunction When stopped Always

all lights interior on after engine shut off.The interior light delay no longer working to turn off after a minute or two.Must disconnect the battery to turn the interior lights off.Dimmer button is in low position and not in the full on position.

You may have a faulty switch at one of the door latches or the latch itself is not fully engaging.Try and lubricate each of the latches and close the door a few times to work the lube in.After you have worked them a few times,close the door slowly.You should hear two clicks from the latch,if not it is not fully engaging.If its not engaging then its not able to tell the switch attached to it that its shut and tell the timer to count me down.If it does engage fully then the switch itself might be bad on one of the doors.Try the lube and see what happens and let me know and I'll try and work you thru if it needs to go further,
Good Luck,
Paul

Lubed all switches 4 side doors and rear double door.Used three in one oil on all switches.However did not hear clicking noise as the door is closed on the door switch at any location.The problem is solved.Lights are turning off on the interior after a minute or two.?Thanks for your help.If i do not hear the clicking do i need to address this issue.

The clicking I speak of comes from the latch itself.If you were to open the door and take a large screwdriver and push in at the jaws of the latch you will hear one click.As you push harder you will hear a second.This is a fully engaged latch which trips the switch.The lube most likely loosened things up.If it reoccurs a closer look may need to paid attention to the latch or swith in question.Glad to be of some help.
Paul

Thanks so much for your clear explanation.Hope we can hook up again on more mechanical questions.What are your specialties.E mail [redacted]

I have over 25 yrs in the automotive industry.I'm a certified Master Technician in auto body and paint.Mechanical is one aspect that every tech needs to have some knowledege of to gain master qualifacation.Again,glad to be of some help and if ever the the need arises,Ill do my best to assist.
Good Luck,
Paul

Thanks Paul for your help.Hope I will connect again for more automotive issues.

Will try when I can.
Good Luck,
Paul

1994 GMC Suburban All Part Groups   

Driving down highway this morning, started up a hill w/ cruise on and began loosing power, electric system still on just couldn't accelerate. Had to pull over, turned vehicle off, restarted & drove okay. Then on way home on highway, fine until went up hill then started to loose power but not complete - could get it to accelerate enough to make it up, definately not accelerating normally. Seemed like it worked hard to shift, but it did manage. Suburban did some slight shaking and the engine sounded like it was working very hard, like a high idle sound while I was driving. The RPMs never went over 3000. Help, we don't know where to start our troubleshooting.

At this point I'll assume no check engine light came on while the engine was running. Also that there was no misfiring, simply a lack of power.

For this start by checking fuel pressure with a gauge. If low, and the fuel filter is overdue to be changed, change the fuel filter. Let me know the results of the fuel pressure test. AutoZone may have a fuel pressure gauge that they loan out (for a refundable deposit, call ahead).

There is also the possibility of a plugged exhaust (IE- catalytic converter). Check this by temporarily dropping the exhaust enough to relieve back pressure, or removing an oxygen sensor. If the problem is with restricted exhaust, you'll notice an immediate improvement in power. Be care as exhaust gases can enter the cabin when you create a leak.

1991 GMC Suburban Ignition System   

I have a 1991 gmc suburban 1500, 350, auto 4x4, a/c & all options (van conversion)....I had it in 4x4 this winter & romped on it (engine had been warming, but was not at operating temperature) & then it started to run horribly....no power, wanted to die, etc....The next day it still idled rough, but ran better..sporadically, it would run horribly, backfiring through the throttle body... I checked the plugs, wires, cap, rotor & replaced them due to corrosion- I thought that would fix it, but it did not. The truck would not throw me any codes.....all coil parts ohmed out appropriately...the distributor shaft was near locked up, so I put in a new performance distributor, but still have the same issue. I was driving it a couple of weeks ago and, sitting at a stop light, it acted like it was going to die...and then it obviously went into bypass mode & the check engine light came on....barely would drive, but got me to church. After church (about 1.5 hrs), it started up & drove like it has since the first issue (rough idle)and the check engine light was no longer on. When I got home, I checked for codes and it gave me a 42. Some so-called mechanic said it could be clogged injectors & charged me a diagnostic fee. I'm done with guess work....this really looks like an electrical issue, but I am stumped. I love my truck, but I hate driving it...it smells of unburnt fuel in the exhaust (though no smoke) and fuel economy has plummeted.

Thanks.

-Bill

Hi Bill,

The problem with code 42 it is electronic contronic module or ignition pick up coil.Both of these parts are located inside the distributor.
Good luck.
Peter
ps;Auto technician for over 30 years.

Thanks for the reply....however, the entire distributor has been replaced, with the same symptoms (module & pickup are matched & came with new performance distributor)

Hi,

Then try crankshaft sensor.

Peter

Now we're back to guessing, and that's what I was trying to get away from by trying this site...a 1991 GMC V1500 4x4 Suburban with a 5.7 350 does not have a crankshaft position sensor.

Hi,
Then you have to take it to a professional.You need someone who can check locally,on the spot.Someone professional.In this situatioan over the internet it is difficult.
Peter

Hello, Carb or fuel injection please?

If fuel injected a code 42 suggests that the PCM detects an open or grounded Ignition Control or bypass circuit.

Do you have a wiring diagram for the Ignition Control?

I'll try to help,

Roger

Apr 26/07 11:29AM: "Hello, Carb or fuel injection please?

If fuel injected a code 42 suggests that the PCM detects an open or grounded Ignition Control or bypass circuit.

Do you have a wiring diagram for the Ignition Control?

It is a 1991 TBI Injection 5.7 350....it only set the code 42 once I have a chiltons wiring diagram.

Thank you. If that code set only once and is not current I'm not going to give it much weight.

Tomorrow I'll have access to the Mitchell 1 Automotive Repair Data Base. I'll research for answers there.

If that doesn't work for you please release the question and someone else may have an answer sooner.

I want to find out why that engine is running so rich that the exhaust will cause your eyes to water.

Roger

If you will provide me your email address I'll send you info from Mitchell 1.

Of all the things I see and based on experience I would first pull the hose off the MAP sensor and see if you can blow back through the throttle body. Its common for a blockage to develop that prevents proper operation on the MAP sensor. It may not set a code.

If its stopped up I remove the throttle body from the engine and clean out the vacuum port using choke cleaner and a short piece of speedometer cable in a cordless drill to route it out.

If no restriction is found unplug the MAP sensor electrical connector. If the engine running improves then replace the sensor.

Will this help?

Roger

My email is [redacted]

I will try your suggestion tonight.

Thank you.

I sent you eight pages to review.

I based my research on rough idle and heavy exhaust fumes.

Roger

Hi, What is the status here please?

Thanks,

Roger

Hi,
Still the same...I took it in to a shop and they said something was telling it to run rich, yet the O2 sensor is working fine....they wanted to replace the fuel pressure regulator, but I'm not fine with swapping out that part unless they can tell me for a fact that the pressure is off (which they didn't)....I'm just waiting until I finish another project vehicle so I have enough money to send her to the dealership....unless you have any other ideas.
Thanks.

I'm on your side. If the fuel pressure is off the test gauge should indicate so.

After our discussion so far I'm expecting to hear that the throttle body needs overhauled....and that would include a fuel pressure regulator and a good cleaning.

Neither you nor I tolerate guessing very well. Given the lattitude to "try something" the throttle body would be my focus.

Roger

Thanks for the input....the only other weird development that I found was that the A/C compressor won't kick in anymore...I can jump it and it will go, but not from the cab control. I did replace the heater core last year, but I thought I ran the A/C after that.....I couldn't find the path on my diagrams, but is that controlled in any way/ shape/ form by the computer?

Thanks.

Should be a low pressure/cycling switch on the side of the accumulator. Unplug it and jump the two wires together with a paper clip or jumper wire.

Does the compressor run? Does the system cool properly? If so replace the switch. It screws onto a valve core so evacuating the system is not necessary.

If the compressor engages but there is insufficient cooling connect gages and service the freon level as needed. Leak test the system as required.

The computer controls compressor cut out at wide open throttle, high power steering pressure during parking maneuvers that the steering is against full travel stops, and turns on electric cooling fans if equiped.

The a/c should run when defrost is used in cool weather unless the computer has a temperature threshold preset (usually 50 degrees F if applicable).

Roger

That was it!! Thanks a bundle...at least one less thing I'll have to worry about...I'm getting ready to bite the bullet and just get a new/reman throttle body, but do you think that would be causing the weird random misfire (can pull off any single plug wire at distributor and runs the same)? Or can the computer malfunction in such a way as to cause my symptoms?
Anyway, thanks again for all of the time and effort you have spent on me....you're the best source of information I've found since my father-in-law moved away 10 years ago.

"Can pull off any single plug wire at distributor and runs the same"? Really?

If the computer were messing with the milisecond timing of firing the two injectors it would be a first time for me.

Two injectors feeding two banks of cylinders and pulling ANY wire makes no difference in the running means the problem (when present) doesn't favor either bank at all. That bugs my eyes out!

Could this engine need the cylinders decarboned? Is pre-detonation going on at full operating temperature after the engine is stopped for 15-20 minutes and is restarted?

Tight clean connections to the computer and good clean tight grounds are a must or the computer may act up. But you know....,unless liquid gets into a computer, the connections are rarely the problem.

If you are ready to turn me loose plaease close the question or click on the OK TO PAY MECHANIC button.

Thank you,

Roger

1990 GMC Suburban Fuel System Tuning When starting When warm 

sometimes when i start truck on a warm start it be sluggish,coughing and alot of black smoke comes out of tail pipe. i change my oxygen sensor, i rebuilt throttle body and adjusted it by turning up rpms. i do not know what else to do.

Hi:
You might want to check your map sensor. Make sure the vacuum line is connected and make sure sure it has plenty of vacuum. Also might want to pull the codes out of the computer to see what it tells you. Good Luck Les.

the code that always come up is for the oxygen sensor. and i changed that before and the map sensor and the other other two sensor that goe on the right side of the throttle body. still the same problem. when problem occurs it goes away after i drive a little bit. the chilton book said that the oxygen sensor does not have to be change sometimes,cause something else is making the code come up for the oxygen sensor causes it to mess up for the time being. i changed alot of sensors and rebuilt TBI. could it be my catalaytic converter. i seen this liquid you pour in your gas tank that suppose to clean your converter or do i need a new one?

Hi;
Might want to check your timing. I have not had any luck with that liquid stuff to clean out the catalytic. Also might want to check your coolant temp. sensor. If its telling the computer that it is below the actual temp. The comp. will compensate by adding more fuel. Thanks Les.

1990 GMC Suburban Electrical / Lighting Systems  When driving Always

battery charge indicates low battery down when I turn on rear a/c fan. The windshield wipers turn on shortly as I turn off the ignition. The alternator is putting out 46 volts,rather than 60 (amps?) as tested at autozone. Short circuit? Where?

Does the alternator actually put out 46 volts or 46 amps? 46 volts would an indicate a severe overcharge condition and it's likely the vehicle would not run.

Is your truck idling when the low battery light comes on? If yes will the low battery light go off if you raise the rpm's? If, yes again alternator output may be low. Try turning on the headlights and windshield wipers (rear blower off), does this turn on the low charge light while idling? If this does alternator output is insufficient (let me know if you hear the belt squeel). If the condition only appears with the rear fan on, the fan could be drawing excess amps (test with an ampmeter) or there could be a short anywhere along the circuitry. The only way to find is to start at the switch or fan motor and work your way back.

the alt was tested when pushing on the gas pedal to run fast as the tech said to do with nothing running

alternator putting out 46amps when tested at fast idle with no accessories on.I tested the vehicle with the headlights and wiper on and everything was ok until I turned on the a/c alone. Even while driving,the battery indicator goes low with a/ c on.

Okay, first try disconnecting the electrical connector to to A/C compressor (this is under the hood and operated by the engine belt). Now turn on the A/C, do you still get the discharge? In this test the fan will still work but the compressor will not be operating (no cold air). This will help to identify the AC compressor/clutch as the problem or the actual fan/blower circuit.

Hey,I went to my genius mechanic and he found that a wire to a spark plug was lying on the engine and got fried on the bottom and had shorted out!(But the diodes on the alternator are bad and its slowly dying anyway) I think I might be okay now. Thanks for your help! Electrical things are awful!

I'm happy to hear you have the problem resolved. Did you notice a running problem at all with one cylinder not operating? I bet you noticed an improvement after wire replacement.