Bulb should flash and stay on as soon as you turn the key to "run". If it does not, that problem needs corrected for sure.
CK5
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tbi to carb ??
- Thread starter dheavychevy38
- Start date
bp71k5
3/4 ton status
Isnt 10psi pretty low for TBI? I thought 12-14 was the proper range. I have to run mine at 16psi.
9-13 is GM spec, people have said that 9-10 is low enough to cause issues in how it runs. That's a pretty huge difference in percentage of fuel the injectors are flowing IMO, and that could show problems under open loop (cold start-idle, WOT).
Didn't have time to do much today but i charged the battery and now she just fires and dies unless i keep my foot around 1/4 throttle.. Hope to work on her tomarrow.
Vacuum leaks?..
Stomis
Professional Amateur
Yep vacuum leak, could be a stuck EGR, or MAp sensor.
Can either of these be capped off just for testing purpose ??
Not sure if you can block off a MAP sensor,it'll run weird if at all probably, if you did..
The EGR valve vacuum hose source can be plugged off,but it might not do anything--the valve itself has a plunger that re-routes exhaust gases from the engine, back into the intake manifold to be re-burned,and when that plunger sticks open,or gets prevented from closing due to carbon chunks under it,it'll let the exhaust flow in the intake constantly,whether the EGR is hooked up or not--that'll act like a vacuum leak (well,it IS !),but worse,because its not just fresh air getting in,its already burnt exhaust ,which dilutes the air fuel mix more than air alone will..and the engine will not want to idle,the idle air control valve will try to compensate probably too,might make it "hunt" up and down or stall.
Taking the EGR valve off and bolting a block off plate over the openings in the intake is about the only way to see if it was letting exhaust go by all the time..
Also check ALL the vacuum hoses going to the intake,like the PCV valve,(make sure that works and isn't stuck open)--brake booster,charcoal canister,etc..any leaks in those,especially the larger hoses,will cause stalling at idle...
The EGR valve vacuum hose source can be plugged off,but it might not do anything--the valve itself has a plunger that re-routes exhaust gases from the engine, back into the intake manifold to be re-burned,and when that plunger sticks open,or gets prevented from closing due to carbon chunks under it,it'll let the exhaust flow in the intake constantly,whether the EGR is hooked up or not--that'll act like a vacuum leak (well,it IS !),but worse,because its not just fresh air getting in,its already burnt exhaust ,which dilutes the air fuel mix more than air alone will..and the engine will not want to idle,the idle air control valve will try to compensate probably too,might make it "hunt" up and down or stall.
Taking the EGR valve off and bolting a block off plate over the openings in the intake is about the only way to see if it was letting exhaust go by all the time..
Also check ALL the vacuum hoses going to the intake,like the PCV valve,(make sure that works and isn't stuck open)--brake booster,charcoal canister,etc..any leaks in those,especially the larger hoses,will cause stalling at idle...
Battery charged up and all vaccum lines along with a new pcv installed. Truck fires up and idles for a little bit so I moved it around the driveway. Everything seemed ok. I let the truck get up to temp and parked it. I tried a restart right after I shut it down and the truck does not start. All I get is cranking and then I noticed massive clouds of white smoke from my exhaust that smell like gas.
Got it to start again but died and no restart again. Ck engine light is on but wont display codes when i jump the a and b terminals. Is it possible the timing could be causeing this ??
Stomis
Professional Amateur
Have you ever changed the ignition module?
Negative
Stomis
Professional Amateur
No restart on hot with no spark screams ignition coil or module to me.
F-ingrob
Wheres the mud
i dumped the TBI due to lack of power and built a new motor around the power that i wanted and now run a carb.
i have 400HP ant the wheels it great off road and in the rocks
and i dont have to worry about the TBI BS that happens
i have 400HP ant the wheels it great off road and in the rocks
and i dont have to worry about the TBI BS that happens
That's too bad.
Martin
Martin
Stomis
Professional Amateur
What he said.
Don't throw parts at this, just a word of advice.
Agree that no spark when hot should be ignition (module solely controls spark on crank) but not throwing a code 12 at a minimum indicates you've got something else wrong too. I wouldn't lean towards a bad ECM, but I'd use the factory service manual to diagnose a no code 12 condition.
No spark condition (which would be the same problem with a carb BTW) can also be diagnosed with the factory service manual. If you DO find a bad component in the distributor, anymore it's fairly wise to just replace the whole thing for ~$100 if the components are all original (or unknown condition), as the components alone cost more.
Agree that no spark when hot should be ignition (module solely controls spark on crank) but not throwing a code 12 at a minimum indicates you've got something else wrong too. I wouldn't lean towards a bad ECM, but I'd use the factory service manual to diagnose a no code 12 condition.
No spark condition (which would be the same problem with a carb BTW) can also be diagnosed with the factory service manual. If you DO find a bad component in the distributor, anymore it's fairly wise to just replace the whole thing for ~$100 if the components are all original (or unknown condition), as the components alone cost more.
The check engine light is on when running but when I try to read the codes by jumping a and b termianls I don't get anything at the bulb. The only thing I have bought so far is some hose so it's not to bad.
Don't want you to get distracted from your no-spark issue, it will never start without spark, but...
Hop in the truck, turn key to "run" (not start). Light should blink on/off/on and stay on until truck is started. If light does not blink, you have a problem. The fact that it stays on when running indicates the same. You'll need to resolve that at some point, but your no-spark condition needs fixed first.
The ECM is completely out of the picture when it comes to spark and the engine turning over to start. Under 400RPM (cranking), all spark is handled with the ignition module.
Hop in the truck, turn key to "run" (not start). Light should blink on/off/on and stay on until truck is started. If light does not blink, you have a problem. The fact that it stays on when running indicates the same. You'll need to resolve that at some point, but your no-spark condition needs fixed first.
The ECM is completely out of the picture when it comes to spark and the engine turning over to start. Under 400RPM (cranking), all spark is handled with the ignition module.
Got a new module gonna try to put on when I get home from work. I don't think the light comes on at all unless the truck is running 
