Fuel pump failure - any advance warning/symptoms?

[LittleCaesar]

Here is a read for you, if the injectors are leaking they may be the problem:
Hard/Long Start When Cold - YotaTech Forums

I take it all grounds are good and clean/tight? One has to worry when previous owners go shadtree mechanic when they have no business doing such...

 

[TheDurk]

The FSM I am referencing (RM887U) has both values listed - 0.2 - 0.3 Ohms AND 0.2 - 3.0 Ohms.

Neither of which are remotely close to the two brand new pumps I received, FWIW. Thanks though.

My paper '99 FSM has the same inconsistent specs you cite. There is no way it should be kOhms, just way too high and at .3Ω @12v it would draw 40 amps, and the fuse and wire are way too small for that. At 3Ω, it would draw 4 amps, and that seems most reasonable at 48 watts. 30Ω means 0.4amp, and that seems too small, that's only 5 watts. V=IR is Ohm's Law.

So I'm going with 2.0-3.0Ω. You sure you read the scale correctly? DMMs can be tricky.

 

[gamefreakgc]

...Ω ... Ω.

Oooh fancy text icons. Teach me your ways of the forums!

On a more serious note, Something's up with the FSM for sure then! 0.2 ohms makes no sense, you'd have to have a really, really sensitive meter to read that low so I agree.

Anyway, this is all just minute details, what's more important is that you found the problem and it's fixed!

 

[mckennar]

I take it all grounds are good and clean/tight? One has to worry when previous owners go shadtree mechanic when they have no business doing such...

The main battery-to-frame ground cable was garbage when I first bought the thing. I replaced that section of harness with the one from my parts car, and cleaned the connections when I did. I've since gone through all of the grounds on the outside of the vehicle starting from the core support and working back, along with a few common ground points inside just to clean them up with a wire brush. I should mention that I consider the crank time before fire on a cold engine to be long only because its long-er than my previous 3rd gens. And I consider the crank time before fire on a warm engine to be too short because its shorter than when cold on the same vehicle, when all of my other 3rd gens were consistent whether hot or cold.

My paper '99 FSM has the same inconsistent specs you cite. There is no way it should be kOhms, just way too high and at .3Ω @12v it would draw 40 amps, and the fuse and wire are way too small for that. At 3Ω, it would draw 4 amps, and that seems most reasonable at 48 watts. 30Ω means 0.4amp, and that seems too small, that's only 5 watts. V=IR is Ohm's Law.

So I'm going with 2.0-3.0Ω. You sure you read the scale correctly? DMMs can be tricky.

I appreciate the info, I am familiar with the scale and how to operate a multimeter. As I mentioned previously, I didn't believe what I was seeing either, so I checked my meter on a resistor, and also during troubleshooting checked cam and crank position sensors among others and they came out within spec on both my el-cheap-o Craftsman DMM and my Fluke 115 from work.

Longshot here but the only difference between testing environments were that I checked the old pump by back probing the connector (there's a little latch you can pop on it) while it was still in the vehicle - I did this so I could test resistance and ensure 12v was hitting the pump. I checked the new pumps from the pins directly on the pump (I mentioned the 4-5 pins on the connector in an earlier post for simplicity, but my assumption is that it's a straight shot from the connector on the top of the fuel tank and the connector where it plugs into the fuel pump inside the tank).

Any chance those pins on the pump are coated in something like an insulator that is "scraped off" revealing metal underneath (kind of like brake rotors are shipped?) when plugged in to a connector? That's the only thing I can think of that would explain this discrepancy, and I don't feel like digging back into underneath my rear seat to check resistance via back probe now that it's plugged in, but I may have to now because my curiosity is piqued.

On a more serious note, Something's up with the FSM for sure then! 0.2 ohms makes no sense, you'd have to have a really, really sensitive meter to read that low so I agree.

That's what I was thinking... I was getting that kind of resistance (0.1 - 0.2) touching my probes together for a baseline so I was wondering how it was going to be accurate.

 

[TheDurk]

I appreciate the info, I am familiar with the scale and how to operate a multimeter. As I mentioned previously, I didn't believe what I was seeing either, so I checked my meter on a resistor, and also during troubleshooting checked cam and crank position sensors among others and they came out within spec on both my el-cheap-o Craftsman DMM and my Fluke 115 from work.

I did not mean to insult. I deal with all levels of electrical expertise on here and I sort of assume idiot until I know better. Saves time. I know better now.

Turns out I was wrong about the pump resistance. I grabbed my old pump from my trail spare box. It was pulled as PM this summer while working perfectly because I had the tank out for my frame swap. It ohms out at 41.7Ω. Go figure...as they say in Brooklyn.

Makes me glad I changed it, anyway.