avhart

Hi again everybody

My 1993 LS400 is not starting due to an ECU problem. My question is: is it ok to run 12v directly to the fuel pump from an outside source in order to start the car? What problems can I run in to if I do that? This will not be a permanent thing and only until I get the ECU fixed.

Thanks in advance

Striker223

Fuse it and be damn sure no vapor is going to escape.

avhart

Hahaha yea escaping gasoline vapor wouldn't be the best thing would it? Thanks for your answer and the fuse is a really good idea - I didn't think of it.

Thx again
Anthony

Yamae

You can try it to try to start the engine but there are 2 issues you need to know.

Once the engine is started, you need to insert the fuel pump resistor 0.7 ohm to reduce the current to the fuel pump motor's current line. The resistor dissipate at least 36W of heat and you should be careful for that. ie: Voltage drop 5V --> P=E X E / R = 5 X 5 / 0.7 = 35.714

Another item to need to know is that there is no protection function done by the circuit opening relay. As long as the engine itself has no problem, you don't need to worry about this.

avhart

Once again, Yamae, you have come to my aid. That is just absolutely vital information that I was totally unaware of. I did some internet research before getting on the forum and although I found that the direct 12 volt supply would indeed work but there was no mention of the pump requiring a voltage drop resistor once the car has started.

This kind of information can only be found on a forum such as this one and only from someone like you with in depth and expert knowledge of the subject. Once I get it going I would post an update because I have some more information about that USA spec ECU I was supposed to try. Remember?

But for now a hundred thanks
Anthony

avhart

Hey guys, I have another question. When I took the original pump out the bracket was pretty rusty. Well I cleaned it up by wire brushing and I would like to know if I should coat it with anything before I put it back in with the new pump.

Thanks
Anthony

avhart

For all who may be interested. I bought a new fuel pump and strainer from eBay and installed it and that solved my starting problem. I didn't need to disconnect it from the circuit and run it on an external 12v source after all. The ECU I am using is not working well and causing the engine to surge up and down but at least it can start the car and pump up the suspension.

I am sending the other ECU up to Automotive Scientific in the US for repairs starting Monday 11th. I will let you guys know how that works out when I get it back. Thanks Yamae for all your help.

Anthony

Yamae

Thanks for the update, avhart. So it was the fuel pump that was causing the non starting problem.
Anyway I hope your ECU will be fixed and you'll enjoy the car ride again.

avhart

Thank you Yamae. I never knew you couldn't send a short message with like two words (the first two). This one should pass the test lol.

Anthony