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School me on relays #4099529 05/17/16 08:11 PM
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Leo99 Online Content OP
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My Rav still hesitates to start when it's been sitting overnight. Not the battery, not the starter. I'm going on the theory the fuel line is losing its prime overnight. I don't hear any fuel pump sounds when I turn the key on but don't start so I suspect the EFI relay might be on the fritz.

From what I read, the EFI relay sends power to the fuel pump at start up. After that, what I read said the fuel pump gets its electricity from another circuit and the EFI relay doesn't do anything. Does that sound right to you?

Looking up the replacement EFI relay, I've seen RY302 and 20382. Picked up a 20382 at Autozone. The box it came in say 20382 but the relay itself has a bunch of other numbers on it. All the relays look alike, are they different inside? I mean besides big amp side open with the small closed or big amp side closed with the small side closed. What do all the numbers mean?


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Leo99] #4099537 05/17/16 08:24 PM
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eljefino Offline
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A relay turns a small current into a large current.

Computer transistors (semi-conductors) want the fuel pump to run, but would burn out powering it directly.

So it powers (usually grounds, actually) a relay's coil which is an electromagnet that closes "bigger" contacts that allow the main current to do its job.

Back in the 80s GM cars used to run the fuel pump off the oil pressure switch, except for four seconds at the start when the relay did the job. If the relay conked out you could crank the engine until it had oil pressure then it would run. Your yota could have the same deal, but, probably not.

The typical diagnosis is to see if you have power exiting the FP relay, as it could be something computer-y or anti-theft-y blocking it before you drop the tank and look for power *there* just due to convenience.

Your typical "4 pin" relay is often called a "bosch relay" and it's pretty standard with bunches of part numbers that interchange. An optional fifth pin lets power out only when *unpowered*. If toyota didn't want a bosch relay inserted, they'd alter the pinout or put a plastic blocker tab in so you had to use their spec relay.

Re: School me on relays [Re: Leo99] #4099546 05/17/16 08:34 PM
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Leo99 Online Content OP
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Thanks, I was hoping it's the oil pressure switch thing but I fear it's not. I didn't hear the fuel pump with the new relay, either.

It's a typical 4 pin relay.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Leo99] #4099558 05/17/16 08:47 PM
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Wheel Offline
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There are some standard number relays, others you need to find the data sheet for - there's a great write up here http://www.12voltplanet.co.uk/relay-guide.html

I think you may see other issues with a bad relay, like random cut-outs while running. How is the fuel pressure ?


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Re: School me on relays [Re: Leo99] #4099560 05/17/16 08:48 PM
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tomcat27 Online Content
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do you have a fuel pressure tester? or borrow one?


2019 Cherokee, 2018 Jetta, 2014 Sentra, 2001 Camry, 1995 Escort, 1970 Cougar, 2013 XT250, 2010 Vstar, 2014 CTX1300
Re: School me on relays [Re: tomcat27] #4099572 05/17/16 09:03 PM
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Leo99 Online Content OP
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Originally Posted By: tomcat27
do you have a fuel pressure tester? or borrow one?


I'd get one but I don't see a fuel line pressure port. I'll have to pull the air box off and look for one.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Wheel] #4099581 05/17/16 09:17 PM
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Leo99 Online Content OP
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Originally Posted By: Wheel
There are some standard number relays, others you need to find the data sheet for - there's a great write up here http://www.12voltplanet.co.uk/relay-guide.html

I think you may see other issues with a bad relay, like random cut-outs while running. How is the fuel pressure ?


My wife says other than the hesitating to start, it runs great. She drives 55 miles each way to work; mostly highway speeds.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Leo99] #4099610 05/17/16 09:55 PM
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Have your wife turn the ignition to the "on" but don't start leave it on for 10 seconds. Turn off then back to on for 10 and see if it starts immediately.

If you suspect Power loss start by checking for parasitic draw with a multimeter. Shouldn't have more than something like 40 miliamp draw with all modules at rest.

Last edited by Superflop; 05/17/16 09:58 PM.

2002 saab 9-5 2.3t wagon
2014 dodge grand caravan
Re: School me on relays [Re: Superflop] #4099612 05/17/16 09:58 PM
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Leo99 Online Content OP
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Originally Posted By: Superflop
Have your wife turn the ignition to the "on" but don't start leave it on for 10 seconds. Turn off then back to on for 10 and see if it starts immediately.


She tried that with the old relay but it didn't help any.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Leo99] #4099629 05/17/16 10:38 PM
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Have you heard the FP previously when all was well? You indicated that a NEW FP relay didn't help, correct?

How cold is it this time of year in NJ? How old is your coolant temp sensor?

If it's out of spec or defective, a cold engine will be tough to start. Once warmed up though, it'll easily restart.

2cents


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Re: School me on relays [Re: Leo99] #4099639 05/17/16 11:07 PM
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abycat Offline
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I know allot of people say fuel pumps usually work or don't but most of my fuel pump failures have been a slowly dieing pump. a fuel pressure test would tell you what's happening at least.


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Re: School me on relays [Re: Leo99] #4099665 05/17/16 11:42 PM
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Originally Posted By: Leo99
Originally Posted By: tomcat27
do you have a fuel pressure tester? or borrow one?


I'd get one but I don't see a fuel line pressure port. I'll have to pull the air box off and look for one.


As a general rule, Japanese vehicles do not have fuel pressure test ports.


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/U341E
2000 Toyota Avalon 1MZ-FE/A541E
Re: School me on relays [Re: Leo99] #4099772 05/18/16 03:27 AM
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Gokhan Offline
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A relay is nothing but a switch controlled by voltage instead of mechanically. Why don't you just test the relay before you replace it? All you have to do is to remove the relay first and then apply 12 volts to the control terminals and see if the ohmmeter reading at the high-current terminals switch from zero to infinity or the other way around.


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Re: School me on relays [Re: Leo99] #4099883 05/18/16 07:45 AM
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Well, it wasn't the relay. The engine was harder to start this morning than it's even been. Whatever it is, it's getting worse.

It's about 55-60F in my garage overnight.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 370,000 miles
2015 Camry 70,000 miles
Re: School me on relays [Re: Leo99] #4099890 05/18/16 07:50 AM
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supton Online Content
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Cranks normal, just no fire; or cranks but tries?


2011 Toyota Camry, base, 2.5L/6MT, 187k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 153k, ours
1999 Toyota Camry LE, 2.2L/4AT, 209k, his
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