No start and no power to the fuel pump, help!

[budwich]

now that you have checked / fixed your voltage levels from your battery and along the way (inertia switch), you need to determine whether your fuel pump relay is operating and if your PCM relay is staying operated. If your PCM relay is "clicking", that is your problem. If your PCM relay is operated "solidly", then you need to check the operation of the fuel pump relay ... as mentioned, key off key on (no starting)... let it run til the PCM drops the fuel pump relay... you should "see" this from a "loss of ground" on the LB/O wire going to the fuel pump relay (the PCM grounds this wire to operate the fuel pump relay and when it wants to stop the pump, it removes the ground...as stated earlier, if the PCM determines that the truck ain't starting ... in this "test", you aren't going to "start"... just key on... then after a few seconds, it drops the ground). You want to test this very clearly. If this succeeds, then the system, PCM, fuel pump, fuel relay are doing their jobs and as a result you can then look a bit further.... crank sensor which tells the PCM that the truck is "starting".

 

[CDW6212R]

What I said, check the priming affect of the key on(not start). This takes no tools and no effort, and no time. The fuel pump relay should have been checked before, which is as simple as swapping it with another relay next to it.

Do the little easy, free, fast stuff, then if the problem isn't obvious, check the fuel pressure.

 

[mikesparky]

I definitely agree about checking the simplest things first. I know I get a partial prime since it will start for a second, but that's it. I've turned it on 5 or 6 times checking voltages before trying to start and it's always the same result.

When the key is turned to "on" the relays (pcm and fuel) click on and then almost immediately click off. I've tried swapping relays with no luck. Just to be sure I didn't somehow fry two relays I'll pick up two new ones tomorrow.

 

[CDW6212R]

It sounds like it's time to get the fuel pressure checked. It needs to be at least 30-35psi before the starter is engaged.

 

[budwich]

IF your PCM relay is "chattering" and not staying operated for the whole time that the key is in the "on" only state, that IS your problem.... that relay should stay solidly operated. When your key is turned to on, the PCM relay should operate and stay operated until you turn your key off. This is the only thing that you need to address.

 

[mikesparky]

Thanks guys. I agree with budwich that if the pcm relay isn't supposed to click on and then off then that's my immediate issue. Once I resolve that problem and the pump is priming and still no start I'll worry about the fuel pressure.

 

[mikesparky]

Now, assuming I change the relays and still have the same problem. What would the next step be?

 

[budwich]

just changing things doesn't necessarily solve problems.... use your meter. The PCM relay gets its operating voltage from your "infamous" diode which you changed (I don't believe that they are normally a problem ... they are there for protection against "reverse polarity things"). Anyways, the "driving" voltage occurs when your key is "on". That's it, its either there or it isn't. That voltage should be "stable" with "key on" coming in on the T/BK lead at the relay.... pull the relay and measure the voltage. Have someone wiggle your key and see if the voltage drops or disappears.... it should be stable always.

 

[skoal_mint]

redneck way, make a swtich for the pump, lol

well what have we ruled out so far, and whats left?

go steal a pcm from a junkyard or even buy it off them..shouldnt be more then $40

but most of the time when u got a bad pcm their is no spark or fuelpump

 

[Doubt Incarnate]

I agree with pcm relay. If you get a partial prime its because the pcm stopped telling it to prime, because it died or lost power. There may be a possibility he has a bad igniton switch, a burned spot on the contact, maybe after he turns the key it hits a freshspot and lands on a bad one. you can test the relay itsself by running 12v thru the coils, if they click and hold, they are good, if they are good then what controls the relay is bad.

that concludes about everything i know about car electronics.

 

[mikesparky]

Thanks guys, I've now changed the pcm and fuel pump relays and still no go. The pcm now only clicks on and off with the key so at least that little issue is solved. Unfortunately the fuel pump relay is still clicking off almost immediately after initially clicking open. I didn't have time to check the voltages, but will do after work (I'm expecting the same). At this point I'd like to check the pump and have a way to get the car running. Should I try to run the pump from a switch from the fuel pump relay or from the inertia switch or elsewhere? If nothing else, maybe if I get the truck running there will be another system malfunctioning that will help nail this problem down! After I check the voltages later today I'll post a summary of the info I've got so far to see if there's anything we've missed.

 

[budwich]

OK... now you have moved forward a bit with a PCM relay that isn't chattering. As mentioned, you can use the "red neck method" to "cause" the fuel pump to run by directly wiring a hot wire to the pump (not thru the relay or inertia switch). IF this is successful, then you are basically down to a few "wiring paths". However, I suspect that although you get your pump running, that isn't your ultimate problem.... it is likely sensor.

 

[mikesparky]

Thanks budwich, I definitely want to fix the real issue, just need to get the truck moving. I agree that this probably is not wiring, what controls the voltage to the fuel pump relay? I think that should be the next question since it's still shutting off prematurely. What sensor(s) did you have in mind?

I know that I need a power source and was simply thinking I could run the power through the existing wiring. Prob not the best idea, just trying to avoid running wire.

 

[Texan01]

Longshot here, but have you tested the ignition switch?

I've run into situations where it will start but as soon as you release the key it'll die as soon as you release the key.

I've also seen them fail where you get accessories and no crank.

Try starting it and slowly releasing the key from start and see if it stays running.

 

[budwich]

well... since you hear / see / measure... remember measure that your fuel pump relay is operating and then dropping... you should verify that the ground is being removed by the PCM (going to the fuel pump winding)... basically the ground is removed from the LB/O wire. Again, with just your "key on" test... you don't have to waste your battery trying to start the thing.... check to see if the ground is removed which should happen at about the same time your fuel pump stops running. This is normal as your pump priming timing is controlled by the PCM. However, on a "true start", the PCM should detect engine rotation and put the ground back. That would be your next test... once you have checked to see it drop.

 

[mikesparky]

I'll check for the drop in a minute, but the pump doesn't run as far as I can tell. It only gets a current for literally a fraction of a second, then the relay clicks off.

I'll also give the ignition switch a try, it feels pretty tight but who knows.

 

[mikesparky]

jeeez

Ok so it was too dark to really deal with the fuse block and check grounds, but I did take a minute and hook up a wire from the 12v outlet to the pump. As far as I could tell the pump was running (very quiet pump) and read a little over 12v. The car started normally and immediately died...so yeah, not completely a pump problem.

So now the question is what's left? All I can think of is pcm or crankshaft sensor. I'm about to get all dramatic over here. My girlfriend and my mother are telling me to trash my ex and get a civic or something!

 

[ranzy]

I went through this on my 95 sport. I just pulled into my driveway and walked into the house for less than a minute. I went to leave again and the truck tried to start but died and that was it. I checked the pressure with a fuel pressure gage and it was 0 psi. I replaced the pump the next day and I was back up and running for a while. It did it again about a week later and I knew that all the work I did and the money spent on the new pump was a waste. I figured I didn't get the wires tight enough while installing the pump or something. I started checking fuses and the inertia switch and that seemed to be fine. I found the fuel pump relay and switched it with one of the other relays that are the same near it in the fuse box. That fixed it. I replaced the relay and it has not failed since. That was about a year ago now. Also had to replace my horn relay too. But that is another thread.

Ranzy

 

[Doubt Incarnate]

so maybe we eliminated fuel as the problem. you have everything to start but its not staying running. maybe bad spark, do '95s have an ignition control module? maybe its got a problem with the run command, try swapping it out. excersize connectors and clean them up.

 

[mikesparky]

Thanks Doubt, I was thinking about the spark issue. How would I test that? Just unhook a plug and observe while starting?(prob what I'd do) It looks like I do have an ignition control module. The cheapest one I can find is around 150. Any way to test it before I get a new one? I'll look at the connectors, how do I excersize them?