ok guys and gals, im working on my daughters 98 blazer 4.3 vortec. we put a motor in it back in the fall, due to unforseen issues, just now getting bk to it. have all eletrical hooked up, fuel lines everything, that i know of. now it wont run unless you pour gas into the throttle body. checked the strator valve and have fuel squirting out there, no fuel gauge but seems to be pretty good pressure. has spark, obviously or it wont run at all. im thinking the injectors are not firing. i have checked all fuses under hood and in dash, all are good. pretty sure we hooked up 2 grounds, one is a ground to the body at the bak of the motor itsa braided flat wire, the oter goes rom the batter to the block. however theere is a red wire there under the fuse block out side that is wrapped up but has an eye on it, not sure if that gets hooked some where or not. i replaced the module there bolted onto the coil bracket, still wont run with out gas poured in it. there has to be something im over looking. i drove both blazer right before e pulled the motors, both ran just fine, but hers had a bad rod bearing.any ideas of what i can check or a direction i can go? thanks, brian

 

If it starts and runs when you add fuel, the problem is fuel delivery, not ignition. Just because fuel squirts out of the service port, doesn't necessarily mean it's OK. Correct fuel pressure and acceptable leakdown is mandatory on this engine. You'll need a fuel pressure tester to find the problem. Most auto parts stores rent/loan them and sell them for around $40. This link will walk you through tests: https://blazerforum.com/forum/2nd-ge...eakdown-88305/
Post all 4 numbers and we can analyze them for you.

 

Bought a pressure gauge today will test tomarrow. If it has the 60 lbs at the port and don't leak down the rest should be good right? Why would both the pumps and motors run fine before the swap and now this one wont fire the injectors? This is what I don't understand. Makes me think there is a ground or something I don't have hooked up or the red wire at the fuse box should go somewhere. But it is taped and don't reach anything.

 

When the problem is found, it will answer both of your questions. When you test pressure and leakdown at the service port, you're seeing the LOWER of regulated pressure or max pump output. 60psi regulated is rock bottom spec, but it is acceptable. If 60psi is all the pump can build, there's a problem. Pressure and leakdown must be checked at both locations to get the big picture.

 

got home this morning and poured a little gas in the tb, started it and it kept running, ran for about 5 minutes till I shut it off. going to try again in the morning and see how it does, may have just been a little stopped up or something. how ever I did buy a 50.00 fuel pressure gauge.

 

Standing at the driver's front fender, looking at the under hood fuse panel, there is a stud on the left side of the fuse panel that has a big red wire with an eye held onto it with a 10mm nut. Looking at the fuse panel cover there is an added cover toward the front of the truck with the letters "B +" on it that protects it. That would be my guess as to where that wire goes. It may have been taped off when the engine was removed so it would not arc against anything.

 

hey guys, sorry it took so long to get back on here. have had alot going on home wise, with dads cancer, girls collage and my work no time to get anything done for myself. the fuel pressure problem is fixed, on that blazer, actually right after i got it started and let it run on its own for a little while it got to where it would fire right up with no problems. had a guy want to buy it so i sold it. thanks for the help. i dod have moms 98 blazer im haveing trouble with now. but im going to post a new topic on it here in just a minute.