Hophead

OK I haven't posted up since before I got it running......swap was completed and has been fantastic - I have put 20k km on it already.

Here is the problem....in late summer after a long 2k mile trip I was thankfully not too far from home out fishing - got back to the truck - it would not start. Traced the problem to the fuel pump - I got home by jumping the pump directly from the battery (subwoofer power) - pump would not run through the normal circuit but would run through the direct line to the battery. I replaced the pump and It has run like a champ every since - until last night.

Last night the truck just died while driving down the street and would not start back up again - just like before. THis morning I checked a few things - made sure I had power getting to igniter, MAF etc. - then thought it might be the pump again - so I jumped the pump directly off the battery again and the truck starts right up and runs great.

Once I got home i probed the connector at the pump and read the voltage while turning over the motor - 2-3volts!???- I jumped the pump and started the motor and again probed the connector to the pump - fluctuating between 2-3.5 volts????

Now I rember the last time (see above) I did the same and I had under battery voltage when starting and battery voltage while running. I thought this to be strange at the time - but looking at the "circuit opening relay" it is not a standard relay and at the time I thought maybe Toyota varies the voltage to the pump for some reason??? When I put in the new pump I just assumed the old pump was worn and required more intial voltage/amperage than the stock circuit would provide and therefore would not get going, but of course ran well with a direct line to the battery - seemingly this was confirmed when the new pump ran fine.


So what the heck is going on?? Anyone know what voltage I should be seeing at the pump?

Sorry for the longwinded story-any help is appreciated.

scuba

Did you happen to change the COR ??

mt_goat

I run my fuel pump off a relay wired directly to the battery. I use the factory wiring to actuate the relay. I mainly did this because I had heard that the performace of the pump was very voltage dependent and the factory wiring going to the pump was very small and in my case 13-14 years old. Plus I'm running a bigger fuel pump than the OEM wiring was made to handle. Might consider doing some direct wiring and just use the factory wiring to signal it.

Hophead

Thanks for the reply Mt Goat - After shovel snow all morning I had a cance to open up the dash and access the COR - output at the Blue fuel pump wire at the relay is a healthy 14V - but checking the voltage at the connecter at the pump is 2volts- somewhere along the wire I have a 12v voltage drop! Looking at the schematic it shows one factoy connector between the relay and te pump labeled as "BL1" - anyone know where this is? I back probed the wire into the connector at the pump thinking it might be the source of the resistance - no luck 2v there too.


Goat - any chance giving me a quick break down of how you wired up your standard relay for the pump? What did you do with the wire from the starter circuit and the GY wire that used to go to the 3.0 airflow meter that I took to the 3.4ecm at FC?

Thanks for the replies folks!

syber_kowboy

It is in the IH1 connector at position 6 in a 91 and I'm pretty sure it's the same in a 92. Basically it's the only solid blue wire in the IH1 connector. It might be grounding to something. If you didn't tape it or disconnect it, it might be touching another wire or the body. I was going to use that wire as the power source for my ODBII port. I think it in the old 3.0 system it went back to the diagnosis port on the engine.

RobD

My guess is that wherever that other connector is, you've got a crap load of corrosion.

Do you have the FSMs to figure out where this junction is?

Hophead

OK its fixed. Went searching for were the voltage drop was coming from - I quickly checked teh connector at the pump I had the same low voltage at the connector and on the BL wire just before it so I ruled this out (Bad idea) the second connector is inside the truck as part of a 10 wire loom - as per the FSM - I couldn't be bothered to trace the hole loom so I decided to just run a new wire from the COR to the connector at the pump- bipassing the problem where ever it was.... did this.....then the EFI fuse would blow anytime I tried to start it!

So I have a short some where - lots of testing with a voltmeter it brought me back to te connector at the pump - shorting out internally. Removed faulty connector and she starts right up!

Wow I love wiring!

Time for a

Thanks for the input guys!

scuba

same thingg happend to me..only on the trail.....