i have a 1989 Scottsdale k5 blazer that im really considering changing over from the stock TBI system to a holly or edlelbrock carb. i have a rebuilt 350 that i cant get to start and im not sure of the problem(it was running then sat for a year before i bought it). i rebuilt the tbi and im getting fuel spraying from the injectors and spark from the distributor to the plugs, all itll do is turn over, all the spark plugs are new and fresh gas. if i spray starting fluid in the tbi the truck well sputter and act like it wants to run then die. not sure if its a ECU problem. dont know much about ECU system. im fairly new to rebuilds.
- is there a way i can check the timing if it doesnt run?
- what all would i have to change over to switch to a carb?
- is it more work and money to switch over then it worth?
- if i switch over could i take out all the ECU to just avoid that headache?

any advice or tips that i could use to trouble shoot are more than welcome

 

Pull the valve covers and plugs. Hand Crank the engine with a socket and ratchet until the number cylinder is on the compression stroke. You can watch the Intake and Exhaust rocker arms (Intake/Exhaust Valves are closed- Compression Stroke) feel for air out of the plug hole. Check the timing marks at the crankshaft and pull the distributer cap and the rotor should be pointing at the number plug location on the cap. If the rotor is 180 degrees out than I would double check to make sure you are at TDC on the compression stroke. If it is out you need to remove the distributer and position it so the rotor is pointing at the number one plug. The car should start at 0 Degrees Timing. Once started you can set timing to spec. If the rotor is close to the number one plug than you may just need to rotate the distributer so the rotor is pointing at the number one plug wire location on the cap.

 

What he said.

Don't switch to a carb. Its all kinds of effort and there is nothing to gain.

 

the timing is good. still not starting. im just planning on using this blazer to hunt with and maybe alil mud every now and then if that makes a difference on thinking about switching to carb. its got a 6in lift and 37in swappers not planning on much highway use. and i know carbs alot better id be able to take out most of the censors and electronics that i dont really know well.

 

Carbs dont have the mileage, throttle response, or easy starting that TBI setups have. Ripping that out is the butch way to go. Not in favor of it. Diagnosing over the internet is difficult, as we can't see what it is doing.

-Is it trying to start and cutting out?
-Is it backfiring thru the exhaust? Thru the TBI?
-Is it firing at all?

I'm going to assume a few things here.
-that you realize you have TDC twice in a cycle, and only one is correct for timing, the other will have the distributor 180 degrees out.
-that the valve train is set up correctly, camshaft timed correctly to the crank, rockers set up and adjusted...
-that your distributor is correctly assembled, firing order is 1-8-4-3-6-5-7-2 and turning clockwise
-that your underhood wiring is not all butchered up from idiots working on the truck
-that your vaccuum lines are all in place and nothing is left open

Start over with the basics. You have compression, right? Rebuilt engine better have compression. (Who did the rebuild? Has it ever run since it was built?) If you have compression, fuel, and (correctly timed) spark an engine will run. TBI setups seem complicated but are really much much simpler than other types of fuel injection--remember all those weird sensors you are afraid of do nothing until the engine is running--under start conditions it is running a program in the computer from numeric tables... the sensors replace that info with current realtime info once the engine is running. Your distributor controls the spark AND tells the injector when to pulse.

Have you visually verified spark and fuel spray? Does the engine run if you pour a little bit of gas down the tbi?

 

It comes down to Fuel, Spark, Timing. I would double and triple check the firing order. If you have an inductive timing light you can check for spark at the coil and at the plugs. You can pour a small amount of gas directly in the TBI unit and crank it. If it tries to fire with a small amount of gas you have fuel delivery problem.

 

locke1992, you have two posts about this and the information between them is conflicting. This thread seems to be newer... so is it safe to assume this is the correct one and I posted on the other one for nothing?

 

I heard that the ECM on these is prone to failure. Try diagnosing it at the relays. If the injectors aren't firing that would be a sign to a bad ECM in my mind.

I wouldn't switch to a carb over TBI. I second what derekbroerse said, and there would be trouble with emissions, if that is applicable.