i have an 88 s10 blazer with the 2.8 and was wundering if anyone could tell me y my injectors lose power when it gets to normal temp.....could a crack in the fuel line cause this....thought it might have been the ecm so i got a new one and it still does it thanx in advace

 

How did you determine what your injectors are loosing 'power'? Or is it the whole truck feels like it is more powerful when cold?

 

when it worms up to normal temp it dies so i had a friend turn it over and i was lookin to see if they were spraying but they werent so i hooked direckt power to them and they sprayed........could a crack in the fuel line cause this because of the pressure loss? i just put in a whole new tbi unit and injectors and it still does it

 

ok, so it runs fine from a cold start until it reaches somewhere around the normal operating temp... I don't know a whole lot about the earlier TBIs, but that seems like it drops the signal to the injectors when the enrichment cycle has ended.

Basically, any fuel injected vehicle has an enrichment cycle that puts more fuel into the engine to get it up to operating temps quicker. Same basic principle as a choke, but completely computer controlled. Beyond that, I have no idea what it could be... Sorry

 

thanx... i got it to stay running now for the most part now its poping one of the ecm fuses so i can drive it as long as i keep some spare fuses with me....dunno y its doin it.....thanx again

 

The choke on the old TBI/TPI systems is a temperature device inside the snorkle on the intake (spring steel spring). There is a round opening on the bottom of the snorkle with a silver cardboard piece of tube that runs to the exhaust manifold. Right above that hole is a flap that is spring steel controlled, as the spring warms up, it closes the flap so fresh air is drawn into the snorkle from the front of the truck. Until the spring warms up, the flap closes off the snorkle and the air is coming up that tube going to the exhaust manifold. Notice the tin piece surrounding the exhuast manifold? That traps air between it and the exhuast manifold so it can warm up and this air gets drawn into the engine on cold days and a cold engine.

I suspect you have a wiring issue, plugged injector, or a temp sensor that isn't functioning. There are several temp sensors on these engines, one tells the ecm when the engine is warm enough and the ecm then controls the air fuel mixture via the injectors based on the reading of that temp sensor. Wrong reading, wrong mixture.

I also want to say one of those injectors is for lower rpms/idle, while the other is for higher rpms/wot. Set up like a 2 barrel carb is. One jet for idle/low rpms, and the other for higher rpms/wot. That being true, for whatever reason when you need the higher rpm/wot injector to work, it isn't. Check your wiring, plugged injector, or one of the temp sensors.

Getting any codes????

 

A 2 barrel TBI uses both injectors the same. The only thing that changes is the PPS (Pulses Per Second) - rpm dependant and pretty self explanitory, and the IPW (Injector Pulse Width) - controlled by a number of sensor readings (temp, map, maf) or by a predefined fuel map) and is how long the injectors stay open (in milli-seconds) for each pulse. What Hanr3 says about the 'choke' sort of applies, but I don't think that has anything to do with the problem at hand... I almost wonder if something isn't going hay-wire with the PCM temp sensor at the point at which it should be leaning out the mixture (lower IPWs).

To allow the engine to warm up quickly, the PCM will increase the IPWs, richening up the mixture (much the same way as a choke cuts the air flow to richen up the mixture). The PCM should monitor the temp sensor and lean the mixture out at a programmed temperature reading. If the sensor flakes out, it is possible that the PCM just shuts down the injectors.

A check would be to start the truck cold and unplug the temp sensor. I'll try to see if I can find a location of the PCM temp sensor for you, but I can't make any promises. My resources for the older trucks are few and far between. There should be one (single wire) sensor in the driver's side head and possibly another one in one of the water passages through the intake manifold and it should have atleast 2 wires on it. I guess it is possible for the PCM to use the same sensor, but again, I am unsure.

 

i went out and strted it and let it worm up and now its fine except for the ecmb fuse popping like every 10 min and cant find any short its got me pulling my hair out lol

 

Thanks for the info on the injectors swart. I wasn't sure how they were set up to work.

The intake temp sensor is located in front on the drivers side, like behind the thermostate, it is a two wire connector, and mine ties into my dash gauge. Not sure if I have any more temp sensors or not, would have to look into first.

Typically if your blwoing a fuse you have a direct short, if it happens after the engine is running, could be related to a sensor. As the sensro comes on line it is sending too much juice or shorting out and popping your fuse. Taht would kind of tie into a temp sensor as well, especially if it is the temp sensor popping the fuse.

 

With most sensors getting low voltage from the PCM I would think it would take a MAJOR short in the PCM to cause the fuse to blow. Most all sensors are run off of +5volts for a reference voltage. Even O2 sensors are reference to +5volts for the actual sensor signal, but the newer heated O2s (3 & 4 wire) use +12volts for the heating element.

This problem may stem to a bad PCM and it is possible that a bad sensor has caused both your old PCM and the replacement (don't know whether it was new or not) to burn out the same way.

So you have gotten the truck to run right now (no fuel problems), but it is popping the PCM fuses now. What did you do to get it to run past warmup?