My bravadas giving me some trouble and I was told it could be the ignition module. Where would I find this on the motor, and after I take it out will a parts store or somewhere test it for me?

 

Found it and took it out, Oriellys tested it and said yes it is bad so I bought another one from them. Got home, put the new one in. Truck still wont start. Did Oriellys just rip me off?

 

If the original ignition coil is bad, they gave you a bad coil, or there are multiple problems. If the original ignition coil is OK, they ripped you off. You need to properly diagnose the cause: 1) It eliminates the guesswork, 2) you know what's causing the problem, and 3) it saves you money!

What are the symptoms? What's been done to the vehicle recently? Does the Check Engine light work? Has it been on recently? If so, what DTC's are in memory? Have you checked fuel pressure and leakdown? If so, what were the pressure readings? Anything you can tell us, will help us in pointing you in the right direction. First step is figure out if it's fuel related or ignition related.

 

Still not sure about the ignition coil, but I have been testing other things on the truck... Someone I work with loaned me a tool to hook up and check for spark, and it is getting fire. He also told me to open a little cap on the 'fuel rail' and push a screwdriver tip in to check for fuel and it sprayed out. I also was told that you could take the oil fill cap off and look in the valve cover to see if the camshaft is working the valves, and that would tell you if the timing chain was broke (?) so I did that and yes the valves are working. The last thing I tried was something I got off of the internet. I took the big vacuum line to the brake booster off and poured some gas in, then hooked it back up and the truck started for just a few seconds. SO... I borrowed a fuel pressure gauge and hooked it up yesterday and saw what may be causing some of my problems. The truck used to have a 4.3 in it with fuel injection but it blew and a mechanic put in a motor with a throttle body. The fuel pressure (switch on) is up where it should be for fuel injection (between 55 and 60 ) instead of between 9 and 13 where it should be tor a throttle body.
Also, after I tested the fuel pressure yesterday I was actually able to start the truck and keep it running as long as I was pushing down the gas pedal. It ran rough, kind of a chugging, and died almost immediately if I let off the gas.
Yes the check engine light is on and usually is flashing a misfire, this is what it was doing when this problem developed shortly after the motor was put in. At first it would still run and then it just lost all power - then quit running entirely.
I guess the next thing to do is determine if I need to change the fuel pump out to one that produces the correct amount of fuel pressure for a throttle body... or maybe there is a regulator or something in there that can be adjusted.

 

I just talked to a mechanic friend and he told me that just changing the fuel regulator wont fix it... the computer will 'want' the factory fuel pressure, the pressure req'd for fuel injection. He said that I would probably have to look for a computer out of a throttle body vehicle or a fuel injection manifold to fix the problem. I cant believe the idiot I got to switch motors for me didnt think of this! Maybe he just wanted the fuel injection manifold for another vehicle he had...
I dont know which would be easier, the computer or the manifold. The computer seems like it would be easier labor wise, and I cant afford to put any more money in this thing so its gonna be me working on it whatever I do.

 

Whoa! Time out! Couple of things.... first, post a picture of the "throttle body". There's a SERIOUS amount of work & money involved in changing it over to TBI, doubtful that anyone would attempt it. 55-60 psi is too low for CSFI, (which is what came stock) and most likely why it won't start. Adding fuel to make it start is the clue here. Before you start replacing any more parts needlessly, post a picture of your engine, especially the "throttle body".

 

Ok will do but probably not til tomorow because when I get home it will be dark... the motor that I found for my (former) mechanic to put in already had a throttle body on it, the original had fuel injection. My Chiltons shop manual said the fuel pressure was 55-60 for fuel injection and 9 - 13 for throttle body.
Someone told me today that the reason I was able to start it after checking the fuel pressure was because I had released the pressure on the fuel system. Hmmm.
By the way, does TBI stand for Throttle Body Injection, or Throttle Body Intake? I am not a mechanic - dont know these kinda things.
And thank you for your input!! =)

 

Just a friendly FYI, your Chilton manual is good for learning how to do an oil change, after that, put it back on the book shelf TBI = Throttle Body Injection and it has two injectors mounted in the throttle body and fuel pressure is 9psi to 13psi. The last year that TBI was used in a Blazer, Jimmy or Bravada was 1994, VIN code Z. Your 1997 Bravada came with CSFI, (Central Sequential Fuel Injection). There are 6 injectors centrally located inside the plenum. Fuel pressure spec is 60psi to 66psi and the 8th character in your VIN is W.

 

And here I've always thought the Chiltons book was like the Bible of car troubleshooting, maintenance and repair! My motor came out of a 98 C1500, which I guess would explain how it has TBI... Is there any good reason a mechanic would leave the TBI and not put the fuel injection manifold on the 'new' motor?

 

Chilton??? Bible of troubleshooting??? not even close. half of the information is missing, the other half is flat out incorrect. A couple hundred pages covering 4 or 5 years. GM "dealer issue" factory shop manual, covers EVERYTHING for one year, over 3,000 pages. Find 'em online brand new for ~$50.

98 1500 4.3L is CSFI, not TBI. Does your engine look like this?