95 blazer has to be jumped to start?!?!
 

Hey all, Im new here and not really tech savvy with the newer vehicles. And i have run into a real WTF..lol. I just bought a 95 chevy blazer 4.3 vortex and my problem is that it has to be jumped to start but runs then.. I've had the alternator tested it's good, got a new battery today. tested the battery it's at about 12.3 and while its running the voltage is at 14.7. Checked and cleaned the positive from the battery all the way to the starter (and cleaned up the connections on the alternator) and negative wire all the way from the battery to the block. When it's running its at a higher idle then it should ( or seems that way to me) but seems alright but seems to have a bit of a miss, there's new plugs and wires and the distributor cap is new to I think so i'm at a bit of a loss.. any ideas?.. maybe in the timing?

Its kind of a pain but it may be worth pulling the starter and having it tested as well, then you will have a better idea if its the engine fighting back or not. You should look up starter voltage drop testing on youtube, theres a guy named dan sullivan who has some really good videos on voltage drop testing. You could have a bad contact in the starter solenoid or a bad winding in the starter motor itself, also if you dont have a bunch of money throw around just get another starter from a salvage yard, you can usually get one for cheaper than the core charge on a new one, like 30 bucks.
Your need for being jumped means that your starter circuit is requiring more amps than it should in order to turn the engine, this means that there is either a wire or component in the start circuit with high resistance caused by corrosion or charring or opens in the windings...or the engine is too tight for the starter to turn it, quick check for this one is to try turning the engine by hand with a wrench on the crankshaft pulley.
Another thing i have seen but its rare is the nose cone broke off the end of the starter so the armature had no end support and was laying on the magnets in the starter body which will require tons of amperage to overcome that amount of friction.

Thanks for the reply! ok i'll have to give that try, had heard something like that on the starter doing that but hadn't given it much thought. turns it over good so that makes sense that it's drawing to much so there isn't enough to get voltage to the rest of the systems.. Thanks again :)

Maybe i misunderstood your first post, does the engine turn over fine on just its own battery when fully charged but will not actually fire up and run? If thats the case then you may just have a bad ground somewhere and maybe not supplying enough current to the fuel pump, ignition system or computer.

My guess would be starter, they use bronze bushing at each end instead of bearings. They start to wear and cause slop in the armature making it angle and jam so it needs extra amps. Depending on what starter is in there now you my need a couple of tricks to get it out. There all here on this board.

Well got the battery tested and that's fine.. It turns over on it's own just doesn't start unless you jump it or hook up a battery charger.

Wow ok so it spins with battery you have. Then you add more juice and it will light up.
Fuel pump might be getting tired. Do a fuel pressure test. You can get the gage at autozone for a deposit. The connecting point is something that looks like a 38 with a tire vale in the center if it comes up less then 62psi check the black ground wire from the pump to the frame and clean it up. In fact you could do that even before you test the pressure.

i'm +2 on the starter bets its draging bad enough it's pulling way too many amps robbing voltage from everything else

Yea, have the starter tested for draw while it is in the vehicle, I think autozone does this, or a volt meter with an amp clamp.

More than likely it's the fuel pump getting weak. Check fuel pressure, since it's a 95, the pressure must be no less than 54 psi...Injector poppets won't even activate until minimum psi is met. Sometimes giving the battery an extra jump is enough to push fuel psi to be able to start/activate injectors. Specifications are 55-61 on this setup, plus the fuel system is very finicky as well as any vacuum leaks. Simple and basic testing is all that's needed prior to throwing anymore parts at it. Bogging and hesitation upon acceleration are some of the other early symptoms with fuel pump getting weak. Good luck. Let us know how you make out!

Well gotta an update: sorry it's taken so long for me to update been a bit crazy.. so i finally got a fuel pressure test done it topped out at about 20 psi so yesterday i went though and changed the fuel pump and filter. still won't start doesn't even help jumping it anymore. have no idea where to check now..

Do you hear the fuel pump running? Maybe a bad wire going to the pump? Also, on the 95 the pump and sending unit were seperate parts i think? Do you just replace the pump motor itself or was it the whole thing with wires, level sensor and hose connections?

ya you can hear the pump going. It's a separate pump and sock assembly. double checked my lines today to make sure i put them in the right place, there good. have spark at the coil.

Does the tailpipe smell gassy after you've cranked? Next thing to check if you have spark and the fuel pump is assumed to be good and making correct pressure is make sure you have pulse at the injectors, you should be able to find the harness and check for pulse with a test light while cranking but you will need a diagram of the pinout for the connector and wire colors to know what youre testing, maybe someone else has them handy, i havent worked on one of those for a long time. Also, how does the oil smell? Gassy at all? Have you tried starting it with the gas pedal on the floor ("Clear Flood" mode) Maybe you have a ruptured fuel pressure regulator diaphragm and the new pump is flooding it? Sorry man, wish you were having better luck!

Don't smell any gas at the exhaust. I checked the oil and it was fine and didn't smell like gas either, that was my concern as well. You mean to check to see if the injectors are getting voltage right? Hmm ya i'll have to check that tried the relays yesterday swapped the pump relay with the horn since there the same and same thing.. ya kinda sucks only had thing since the 28th of last monthe and been able to drive it maybe an hour..I really appreciate the help!! any ideas better then having to take it to a shop i know i can't afford..lol

Yep checking for voltage at the injectors, ground a test light and backprobe the connector. Also can you get fuel pressure checked again with the new pump? Aftermarket pumps are known to be junk right out of the box about 15-20% of the time and with the small window of specified pressure you can't assume that its correct, also its possible that the fuel pressure regulator could just be stuck open allowing fuel to return to the tank, this would happen if the spring inside it breaks.

Can you try spraying some starting fluid in the intake, open the throttle plate and spray a good 2 second shot in there and then pop the intake tube back on quick and try starting, that would be an easier test to see if you arent getting fuel, be careful though, fire is possible so be prepared just in case. If it fires up and then stalls you still arent getting fuel, if still nothing then you need to look at other stuff.

I stole this picture from another thread by Cidium about replacing the spider injector and added the caption, its shows where to find the injector connector. Blue and red wires, unplug the connector and probe both wires on the computer side of the harness at the same time with a test light and you should get a blinking light when cranking, this is the safest way to test it, you may have to rig something to connect the test light to both wires though but be careful not to short them together. The only other way is to probe with the test light connected to power or ground but its risky because you can send power into the computers injector driver and fry it real easy. You could also do an ohm test on the pins going to the intake (injector) side of the connector, Resistance should be 1.9 to 2.1 Ohms. If you have pulse to the injector and the injector resistance checks out ok and you can get it to start by spraying starting fluid in it then you still arent getting enough pressure from the pump or the regulator is stuck open. Theres some more things to try, let me know how they turn out.

Ok cool.. that pic helps alot! the pcv valve is disconnected on mine as well, been trying to figure out where it went and now i have an idea lol.

Yeah make sure the pcv valve is hooked up, if the hose is unhooked and not plugged it makes a big vacuum leak and will cause high idle, stalling and probably contribute to hard starting too.

I don't read any place that you have taken the plenum off, it's so simple a dumb ass like me can do it in less then half an hour. You realy only need a deep socket 10mm. If you see shiny gold spots that's were its leaking. Main fuel lines in there like to go for some reason they call it the nut kit. There on drivers side. FPR likes to and that's on the pass side of the cpi. Both parts are not terribly expensive and not hard to replace. Dorman makes them so that tells me they go a lot.

ok if i take the plenum off don't i have to replace gaskets?.. and this is a stupid question but never worked on a vehicle this new do i need to bleed the fuel line?

Yes you will probably need the new gasket if you pull the upper plenum unless the old one doesnt rip, its about $10-15 bucks at most auto parts stores, search for a how to video on youtube for help, theres a good one titled "S10 CPI Replacement (spider)". Not really any need to bleed fuel line unless you plan to disconnect it and you wont have to do that to remove the upper plenum, not much will happen anyway, most mechanics skip that step and just disconnect carefully with a rag over the spot to stop any spray and catch leakage.

Ok that's what i thought.lol.. I just watched that video on youtube was very informative. just figured i'd ask to be safe. ya figure i better take a peak under that plenum for leaks on the nut kit and check the fuel pressure regulator.

Ok.. got an update for ya guys. i took off the plenum and it looked good, was even able to save the gasket :). minus the fact that two of the vacuum lines were not on it. I know the pvc goes to the top of it on the front and got the bottom front connected (it wasn't lol) but i can't figure out where the small one on the back of the plenum goes. I know the big ones goes to the brake booster, got that. Also figured out that i did have a bad ground (the body ground)so i have it to the point were i have spark and fuel and still won't fire, pretty sure it's a timing issue tho.. and being able to jump it to get to start doesn't work anymore, not sure if that's a bad thing or not yet..lol.

New update: Ok i timed it and it fired right up!.. then i noticed the alternator was vibrating a bit so i shut it down to check it and it it wouldn't start back up. Looked at again the next day and decided to re time it, well when i brought it to TDC i noticed the timing marks on the rotor where off so re timed it and put it back together and it started right up again. So i let it run for a bit and after like 5 to 10 mins it started to vibrate and about 15 mins when you would press the gas it started to bog down. kinda weird but from what i have read the camshaft sensor and or the crankshaft sensor can cause that because there sending faulty info to the computer.

Go to google on the bf homepage and put something like "bad distributor" in and see if anything relates.

Ok new update: Well got it all timed in and ran good started it like 4 or 5 times was running nice! Took it for a test drive and made it about three or 4 miles and it was like somebody had lust hit a kill switch, just shut off.. wouldn't start again so i checked the fuel and it's good all the way up to the Schroeder valve behind the intake. will start with starting fluid.. so now its gotta be the spider right?

New update.. if anybody is still reading lol. OK so i replaced the spider or injector assembly and runs good. A bit of a high idle off and on but pretty sure its some vacuum leaks. Thanks for the help guys :)