Hey I just bought a 2000 Jimmy today and it's having similar symptoms. Haven't checked the fuel pressure yet, but it pops right off and runs great with a shot of starting fluid. It seems that sometimes it wants to start with a boost and sometimes not. So I'm not sure yet if it's the battery or pump. With yours starting everytime with a boost, I would definitely have it load tested first before I replaced the pump.

 

yea it starts once it gets that extra kick from another battery. i was going to check all wires down there to see if any of them are grounding out or if i am getting right amount of voltage to the pump. how would i load test it?

 

also @pontiac have you changed the fuel filter? that mite just do the trick, the filter could just be clogged. getting at the pump is a bit of a pain haha.

 

Remove the connections to the battery and using a wire brush and clean all parts of the connections (battery side and cable). check the fuel pressure again, key on but not started. Reason for this procedure is to eliminate the chance that the connections are corroded and not supplying full voltage to the system. When jumper cables are used they bypass the connections to the trucks battery. If you have a multi-meter you might want to check the output voltage of your battery by connecting the red lead to the large lug on the back of the alternator and black to a good ground on the engine or body, but not the battery. It should be above 12 volts DC. If not jump the truck off and let it charge the battery for a while, with the jumper cables disconnected. While the truck is running verify that the voltage is 13.5 vdc or better. Once the truck has been shut off recheck battery voltage at previously mentioned locations. It should be higher than 12 vdc. Turn the key on, not running, and check fuel pressure. Hopefully it will be better and around 60psi. Recheck the battery voltage and fuel pressure again after letting the truck set maybe over night. They should be close to the same. If pressure is still low and you have over 12 volts from the battery, key on not running I would consider swapping out the fuel pressure regulator or maybe the fuel injector spider. The pressure regulator is part of the spider and you have to do basically the same procedure to change. If you do not have 12+ volts then I would recommend swapping a know good battery into the Blazer and see if it makes a difference. It should. Recheck pressure and try to start the engine. Hope that the information helps. As stated earlier by another member the pressure should drop a bit once the engine starts so expect it.

 

Sorry, I went off for the weekend. I'll be messing with mine today. 70Camaroman has some good points. Load testing can be done at most auto stores. It simulates a load on the battery while checking the amps it puts out. It CAN drop. I've charged several batteries that came up to 12 volts, but crap out at the first sign of load. Amps is what actually powers things.

 

Following the above mentioned items do the following load test, if you don't want to take it to an auto parts store. Best way I have found to load test a "well charged" battery at home, unless you actually have a load tester, is to hook up a multi-meter and either have a friend watch it or yourself. Remove the coil plug and crank the engine over watching the voltage and see how far it drops. It will drop. If it drops below 9.5 volts your battery needs to be replaced.

 

awesome, i will try this today. i actually bought a muti-meter yesterday to test charge on bat, 12.26v. i'll test load today and see what happens, but i think its just that pump. yesterday i had me brother turn key on and i listened at the tank, pump sounded weak and tired. ill also test and see if im gettin right voltage back there. will report back with findings. peace.

 

ok i got down at the pump to test voltage to it..it turns on but i did not get any reading. any of you guys know which wire is the power at the connector? i tried to look it up on here but it kept showing me a square looking connector, thats not the same connector i have on my pump. any one know or have a link?

 

OK, I think I have this figured out. Crawl out from under your truck. I checked my truck today. Key on 12.5 volts I have 44 psi= won't run/ Add ****ty jumper cables 13.4 volts@ 50-51 psi= starts to hit but voltage goes down immediately and won't run ( I'm thinking like yours if I had my better cables it would have boosted my voltage better and cranked)/ Hit it with starting fluid to initially crank it and voltage goes up to 14.5= psi goes up to 55 and it runs. So our pumps are so weak that they will produce enough pressure to barely run @ 14 volts but not enough to run @ 12.5 volts. I ordered a pump only off ebay for 20 bucks (this is for sale) Isn't it stange that we have the same problem at the same time?

 

dude! thats exactly the same thing that me damn truck does. well im glad that im not the only one experiencing this (not that its a good thing that you are) i thought i was going nuts or something. i still want to see how much voltage i get down at the pump thou, just want to be sure before i throw the cash down for a pump. those things are ridiculously expensive.