Electrical trouble shooting ???

[RIO5.0]

Maybe someone can enlighten me....My truck took a dump at work few days ago, came out and she was a no start...crank and crank but no fire...anyway had it towed home today....Was running problem free prior to this..
I suspect the fuel pump as its got 116k on it. I threw a shot of gas in the TB and it fired right up. The pumps 287.00...W.T.F.......so I start testing voltage to the pump and I'm seeing something kinda wacky...My test light show "pulsing voltage?? as in the lights on and off like a blinker??? I hook up my volt meter and it show the voltage flucuating also...like 1.3 to 6.5 then up to 11.7 then cycles over again...What gives, never seen nothing like it???

Thanks...

 

[HISSIN50]

Andy, does your fuel pump wiring go through an oil pressure switch (so if there's no oil pressure, the fuel pump doesnt get fire)?

That's the time that I've seen the power to the pump pulse (this was on a GM).

Good luck bud.

 

[RIO5.0]

I think your right..I read in my Haynes that there is a FP relay..it reads " the pump uses relays that are designed so that should the engine stop (causing the alt to turn off and the oil pressure to drop) the pump will cease to operate..

I noticed it the other day when going over the fuses..I have no idea how to test the mother though??? Its a big mother thats fully sealed...other than a continuity test I'm kinda hosed?? any ideas how to test it???

It would appear i have power to the pump. removing the feed from the filter and hitting the key gives nada...This is one of those silent pumps too...never heard the mother in 5 years so that kinda blows on the audio test...

 

[HISSIN50]

I recently went through a crap match like this (on said GM truck - no schraeder valve either so I couldn't check pressure).

Though it was pulsing the current feed, I went on a hunch (100K mile OEM pump) and pulled the tank. I didnt have flow charts so I just compared the two (doing my own flow testing over about 8 seconds of flow-time) and the old one had semi-crapped its pants (on a EFI system that only required 12 PSIG). I was down about 50% in flow, though I still had some pressure at the injectors (I initially tested other crap because I saw fuel squirt ).

Is there a way to jump the pump like on the stangs (how we can jump the self test connector to make the pump run)?

For you otherwise, if you can find a good enough diagram to trace wires, I'd see about removing an electrical connector (like for an oil pressure sending unit) and jumping it so the FP runs constant.

It seems to me that with any amount of voltage to the pump, you see at least see a dribble out of the pump. Can you do a rig and run fused battery power to the pump? This is what I ended up doing - it ruled out the OEM power feed.

I know you know all this stuff - I'm just tryin to think aloud with you bud.

BTW, I cant remember what kind of truck you have (I thought I recalled seeing an older 4 Runner outside your garage.....??)?

Good luck Andy.

 

[RIO5.0]

thanks for your thoughts...appreciate the help....This pump has like 5 feeds to it...thing is its so old, 87 Nissan hardbody with 116k on it, that things are real spooky as far as accessing it...I think its gonna be way easier to cut 6 bolts and lift the bed off then to attempt to even touch the fuel lines or begin to drop the tank, its not a pretty sight...I can see alot of chit breaking here... Even the cover bolts to access the pump are wasted.
The Haynes only has the basic wiring schematics...This thing has an EEC but codes proved nada...theres only 10 or so and none related to fuel...W.T.F.??? Me and a bud both pulled the codes and got a clear code 44...the book gives a 41/43/45....no damn 44.... so I have to search that out...

I'm gonna bring the replay to work and have the electrcians take a wack at testing em...we have like 10 of them that work all the CNC equipment...a relay is only 15.00...thats looking pretty good compared to dropping that tank...
I been down this road before on other vechicles and found it wasn't the pump...there's just so much chit to test...

As said...preciate the input...

 

[HISSIN50]

Sounds good mang. After doing the last pump on that truck, I also thought to myself that pullin the bed out of the way might be easier. It was kind of an SOB to get the tank back up there and make the connections (thanks for having no slack in the lines - I was making unseen hose connections with the tank 90% of the way back in the truck. ). Oooh, I forgot about your lift - that's gotta help though............

This was on a early 90's GM truck - I'd drive it around the block till it stalled - never a code either.
I'm sure you'll have it whipped in no time


Good luck Andy.

 

[tmoss]

I'm sure your electrical guys at work can help Andy. Sometimes taking voltage readings to ground does not tell you what you need to know. In the case of a relay power circuit to the pump, you need to put power to a pump through the relay and measure voltage drop across the relay contacts - i.e. black on pump side of the relay and red on the battery side (or vise versa as it is not polarity sensitive). If the voltage drop is more than .5v or so it's an indication the contact faces are arced up and not a good current carrying connection.

 

[RIO5.0]

I had a gent at work check the relays and he showed me how to test them...I had to put 12V to em first...Had 2 side by each so I had him check it to a known good one...Both are fine he said...

I made and access panel in the bed... Its a beater anyway and I'll MIG the panel back in.

This is what I found...not good...wire was rotted right off and check the bolts out... Not looking to good on getting em out...I can see a new tank in my future...May just be time to send this betty to the crusher... Talk about opening a can of worms...I douched the bolts last night with PB Blaster and walked away....

 

[tmoss]

scary man - gonna take those bolts out?

 

[RIO5.0]

no choice in the matter....thats the access...I know at least 3 are gonna bust right off..Im gonna douche it again tonite...then head out for a few magaritas and to a comedy show...not even in the mood to mees with it...downright discouraging it is...

 

[HISSIN50]

That's horrible. I know you're good Andy - were it me I'd just get a new tank. I have a hard enough time removing those things when they aren't shat all over like that.

Good luck!

 

[blksn955.o]

buddy of mine had a sim. issue with his 88-90 (?) nissan 3.0l 4x4. His tank looked like that as well . That thing turned into one problem after another. Pumps went nasty (clogged) lines as well. Another buddy had one of the limited "desert runner" trucks tons of issues with everything. I had a 93 4banger 2wd and it was a tank (traded it in on the mustang)...I have seen far to many issues with the 3.0 truck.

Good luck man...I have seen and felt your pain.

 

[RIO5.0]

Well I'll be dammned I got the mother out....I douched it for 2 days with PB Blaster, hit it with Vise-grips cause the heads were spent and they broke loose..


I had one wire on the outside that was broke off in the above pic, and I re-soldered it figuring W.T.F. I got nothing to lose and might luck out...No dice..
It seems the ground on the inside also took a dump. The rivet head broke off its connection and it was all over..Sad part is the pump is 188.00 and AZ had that in stock...But I'm screwed as this is a part of the sending unit so it looks like 300.00 for the whole set-up...

 

[HISSIN50]

Who needs a sending unit?

Can you do a work-around and retrofit for just a pump? There's gotta be some better option since this seems like an all-purpose work truck. Between you and Tom, I bet you could come up with something - you're both real creative and Andy, I know you got fab skills.

 

[RIO5.0]

I was thinking of just soldering that connection back in place but didn't know if the solder would hold up in that enviroment?? My luck it would melt off in a few weeks and strand me...

 

[tmoss]

Looks like brass - it will hold up just fine Andy - if you prep the surfaces, which I figured you'd do.............check the others too and solder them if they feel "loose".

Hey, what's that smooth cone in the last pic next to the T-stat housing shaped like a tapered porting bit?

Use some rust-converter on the top of that cover.

 

[RIO5.0]

The more I thought about it I realized all the wires are soldered...DOH.
So I whipped out the soldering gun and fabbed a copper pin soldered that, and then the Brass connector back in place...Continuity test was a pass...hooked it up outside the truck and it pumped fuel right out...
I button it all back up, push it outta the garage hit the key and she came right to life...Then I look out back while its idling and see fuel everywhere....The freakin output tube gave up the ghost..rust got the better of it and it popped a hole right where in enters the housing...back to square one. Gotta go buy a sending unit...DAMN..I was so close...
Thanks for your help guys...Got a nice little lesson on Elec 101 on this one...

This ain't my week for vechicles...had to put 4 tires on the wifes Pathfinder today...that was 600.00, I look under it at the tire warehouse and see the struts leaking all over the place, another 550.00 for struts and shocks, and found a bad ball joint on the pass side to boot, and the pads are about spanked. 70k on it and I never put a penny into it...but now its all coming at once...
I HAD intensions of putting the Mustang back on the road this week but it ain't looking good...

Tom....Thats an arbor for using cloth wheels for polishing...A christmas tree is what I call em..That other pc is an extension I had to make for my F/P gage...I added a 1" spacer for my GT40 upper and had to whip that betty up...

 

[HISSIN50]

Sheesh brah - that sucks. For the wifie's car that's not too bad (I mean getting 70K out of the OEM stuff, sans the BJ - that shoulda' lasted longer).

Now you get to have a fun afternoon of installing supsension and brakes on the Pathfinder. But ya know what - I know that getting on that black beaut and rippin it up to triple digits in second gear makes ya feel better.

 

[SeventyMach1]

Sucks to hear Andy. At least you're making progress on it. Hope you get her straight soon.


Oh, and be careful welding in that vicinity.

 

[tmoss]

Pour a big batch of JB Weld on that thing