89 Blazer Wouldn't Start Now Running Rich

Markgc · 03-05-2006, 01:11 PM

My 89 S10 4.3L V6 Blazer wouldn't start when I was out shopping on Friday. I had it towed home and the engine fired up immediately on Saturday for a brief test. Thinking that it was an ignition problem I fitted a new disrtibutor cap, rotor arm and king lead on Sunday afternoon

It then started up easlily and as I ran the engine I saw that it was running very rich. I backed it out of the shop and when I put my hand in front the the tailpipe even though the mixture was sooty and rich, the exhaust gasses were so hot that it burnt the hairs off my hand - ouch.

When driving back into the shop the engine stalled and wouldn't start again - I only tried briefly to restart this time, since the failure to start a warm engine was the same as I had on Friday when I was out shopping.

Having a rich engine running so hot is strange - I don't know what to look at now. I imagine that some sensor is misbehaving - where do I go from here? I have the shop manuals and am pouring over them.

My service engine light doesn't seem to come on at all - maybe the bulb has blown - is there a way to read any engine diagnostic codes without using the service engine light to flash out these codes? I hate to have to strip out the dashboard to get at the service engine light.

thanks Mark

Markgc · 03-05-2006, 03:54 PM

Going to try changing the MAP sensor first. A couple of brittle EGR control lines need replacing.

Has anyone had any experience with a good scan tool for this vehicle? I think that I need one to read the sensor outputs.

Teal95Jimmy · 03-05-2006, 06:44 PM

On the older 12 pin connecting OBD I systems there is no real need for a scan tool. Assuming your check engine light works you just need to jump the top right and the pin next to it for the computer to go into diagnostic mode. Don't start the truck, just turn the key to run

Markgc · 03-05-2006, 07:05 PM

The check engine light doesn't work and I don't want to rip into the dashboard to fix it. I figured that a scan tool would be an easier way to go.

I should be able to read some sensor data with a scanner shouldn't I - the shop manual indicates that I can read quite a bit of sensor data. Got to beat changing random sensors.

Markgc · 03-15-2006, 05:18 PM

I got a scan hooked up. I found two error codes - O2 sensor saying rich mixture and low voltage from MAP sensor. The low MAP sensor voltage is most likely from diagnostic tests when I ran the engine with the electrical connector disconnected from the MAP sensor. I have cleared the codes but now I can't get the engine to start at all.

I am monitoring the ecm values in real time with the scan tool. The MAP sensor is reading 4.80V and looks about right. The TPS runs from 0.70V with throttle closed and 4.28V with the throttle fully down - this looks a little low. The O2 sensor is reading around 450mV

I cannot get the ECM to go into the Clear Flood mode which might help me start the engine, despite holding the throttle down and cranking the engine the scan tool shows the Clear Flood mode as OFF. I am not seeing any RPM reading when cranking the engine - not sure if this is a real problem or an issue with the tool not reading the serial data correctly. It would help if I could get the engine to fire up but maybe the plugs are fouled from running so rich. I am going to wire in a remote starter so that I can monitor the injector body and spark while cranking.

Does anyone have any further thoughts. I haven't seen any obvious reason fro running so rich yet. Is isn't looking like a sensor to me right now.

Mark

MT-2500 · 03-15-2006, 07:15 PM

Check for good hot blue spark to plugs.
Then check fuel pressure and watch for fast leak down.
Is it a tbi or mpi fuel injection.
To shut fuel off you can unplug fuel pump relay if it will not go into clear flood.
Plull a plug or two and see if it is has gas on it.
But no rpm reading and no check engine light kinda points to the computer.
Drop it down and give it the old tap or twist test and see what it does.
Good luck.
Mt

BlazerLT · 03-15-2006, 10:05 PM

Reset your timing to zero.

Remember to disconnect the timing wire while doing so.

Markgc · 03-16-2006, 01:43 AM

It's the Model 220 T Body.

I am trying to see where to connect a gauge to measure the fuel pressurre. A high fuel pressure would give me a running rich problem.

I don't know why it won't go into clear flood. It says that throttle must be greater than 80% for 20 secs with ignition on and rpm below 600rpm. The manual doesn't say anything about cranking the engine but I have tried both. The scan tool might not be reading right. I would hve to monitor the injector pusles to be sure. The max voltage on the TPS at 4.2V with the pedal top the metal is a little low - I disconnected the tps connector and jumpered across the tps connenctor to apply the full 5v refrence voltage to the tps input pin and the scan tool showed 5v on the tps signal but still I never could see a computer indication of flood mode. The tps is a little off I think too.

How do I reset the timing to zero. I have cleared all the codes in the ecm.

I am going to hook up a remote starter wire so that I can take a good look at the spark and injector patterns. The starter is buried below the exhaust manifold.

Rmbodie · 03-16-2006, 02:38 AM

Good luck , I got so fed up with my TBI on my 89 that I took the whole damn thing off . I beleive the tps calibrates itself when you reset the codes and drive it , but if it will not run that idea is useless .
You may have a problem with the idle air control solenoid . mine would not idle correctly and ran rich when it was above idle speed . I disconnected it and removed it and adjusted it to make it idle and left it loose.
Are the injectors leaking when it is pressurized ? Rob

Markgc · 03-16-2006, 02:55 AM

What did you replace the TBI with on your 89. I have the 4.3l engine. I might consider this since this vehicles no longer requires smog testing in NC

I will check to see if the injectors are leaking and spatying properly. I am trying to figure out what fittings I need to connect up a fuel pressure gauge to monitor the pressure. Is the pump running when the ignition is turned. I have the shop manuals but sometimes it takes a lot of digging to find the right information.

There are 2 injectors in the TBI unit. Are they both on at low running or is one for acceleration. I think the one on the left - ie the passenger side was doing the most fuel injecting when it was last running.

I need to get the thing to start but everything is all sooted up now. Gone are the days when removing spark plugs was easy

Markgc · 03-16-2006, 04:06 AM

I would like to test the fuel pressure - it looks like I have to open up the fuel line where it connects between the flexible lines and the steel line in the engine compartment. I will need some sort of T adapter. Has anyone done this and knows where I can get this adapter. I have a fuel line pressure gauge in the garage somewhere. I will dig it out and see if it has any adapters with it. Goodness knows what the threads are.

thanks Mark

Rmbodie · 03-16-2006, 06:05 AM

I am just south of you in SC . I now have an Edelbrock carb and intake and cam . Power package as they call it . I replaced every sensor and component on the fuel and ignition systems with no success of solving my problem . The kit is listed for marine engines since it does not have EGR capability . Rob

MT-2500 · 03-16-2006, 08:30 AM

Quote:

Originally Posted by Markgc

I would like to test the fuel pressure - it looks like I have to open up the fuel line where it connects between the flexible lines and the steel line in the engine compartment. I will need some sort of T adapter. Has anyone done this and knows where I can get this adapter. I have a fuel line pressure gauge in the garage somewhere. I will dig it out and see if it has any adapters with it. Goodness knows what the threads are.

thanks Mark

The best place to test the fuel pressure on that one is at the fuel filter.
Special fitting on the line so you will need a adapter to fit them.
9-13 lbs of fuel pressure.
Good luck
MT

Markgc · 03-16-2006, 12:35 PM

Thank you both,

I will see what fuel adapters I have got.

I need to remotely crank the engine from under the hood. There is no way to get at the terminals on the starter motor - I think I have followed the wires back - there is a thick bundle and a thin bundle. I am thinking that the solnoid line will be in the thin bundle that comes out in front of the engine (probably only as single wire in the thin bundle). I imagine that I can tap into this wire there. Is there any other place that techs use when they want to remotely crank this engine?

thanks Mark

MT-2500 · 03-16-2006, 01:13 PM

Look for a purple wire a litter bigger than some.
I catch a lot of them around the brake booster are.
MT

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