Engine Management

Tiny
TOPDAD1947
  • MEMBER
  • 1996 TOYOTA AVALON
  • 3.0L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 187,000 MILES
My problem is the car starts for thirty seconds and dies! I have replaced the in tank fuel pump and sending unit plus a new fuel filter and fuel pressure regulator! Car still wont start? I checked all fuses and relays all are working properly. Now I was told by my mechanic that it is the circuit opening relay. Now I tested the connection to the fuel pump and what I found was when the ignition is turned on fuel pump does not respond! When I turn the ignition to the on or start position pump turns on. Let go of switch and car dies. I need someone who knows what this problem is. It has me stumped! Thanks, Tom.
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Friday, September 16th, 2016 AT 4:59 PM

23 Replies

Tiny
CARADIODOC
  • EXPERT
First of all, the pump must not turn on with just the ignition switch on. It will run for one second, but not again until the engine is rotating. The first thing you need to do is check if you have spark when the no-start occurs. Too many people get hung up on the first thing they find missing and fail to look for other dead systems.
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Friday, September 16th, 2016 AT 9:44 PM
Tiny
TOPDAD1947
  • MEMBER
Well I did that. I changed the spark plugs and ignition wires. Any other thoughts? I was told it could be the ignition switch or the circuit opening relay. Your thoughts? Thanks, Tom.
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Friday, September 16th, 2016 AT 11:40 PM
Tiny
CARADIODOC
  • EXPERT
Did you check for spark?

From your original post, it sounds like the Circuit Opening Relay was tested and it is working. Other manufacturers call that the fuel pump relay. If your mechanic suggested that, it is the first thing you should have tried. Normally we do not approve of throwing random parts at a problem, but in this case finding a good used one from a salvage yard to "try" is much less expensive than an hour of diagnostic time. If it solves the problem, we are all happy. If it does not, you are not out very much.

The fuel pump will run for only one second when you turn on the ignition switch to insure fuel pressure is up for starting, then it turns off again. It will get turned on by the Engine Computer when it sees engine rotation, (cranking or running), and it knows that by the presence of signal pulses from the crankshaft position sensor and the camshaft position sensor. Those sensors also are used for injector timing and spark timing. If either sensor fails you wont have injector pulses, fuel pump, or spark. That is why you need to check for spark. About three percent of crank / no-starts are caused by a failure in the fuel supply system, where you are spending all your time. About two percent are caused by a failure in the ignition system. Close to ninety five percent of no-starts are caused by those sensors resulting in no spark and no injector pulses or fuel pump. To add to the insult, those sensors often fail by becoming heat-sensitive. One will fail after the engine has been running and commonly after a hot engine has been off for a few minutes. That eliminates natural air flow that helps to keep them cool. They will work again after they cool down, typically after an hour or so.
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Saturday, September 17th, 2016 AT 12:26 AM
Tiny
TOPDAD1947
  • MEMBER
Okay, I will check spark on cranking. I have the circuit opening relay, but cannot find its location. And believe me I have tried. Passenger kick panel? Behind the radio? Under the hood? Drivers side fuse panel? Behind center console? I gave up at this point. Any Idea Where It Is? Thanks, Tom.
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Saturday, September 17th, 2016 AT 10:36 AM
Tiny
CARADIODOC
  • EXPERT
It is shown as being behind the glove box. Interesting place to hide it.
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Saturday, September 17th, 2016 AT 12:08 PM
Tiny
TOPDAD1947
  • MEMBER
Thanks. Last place I would have thought of. Tom.
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Saturday, September 17th, 2016 AT 1:59 PM
Tiny
TOPDAD1947
  • MEMBER
Well it is not there. Rip the whole dash apart? This is really getting frustrating! Plus if those sensors were bad the car would not start at all. I do not have that problem? It starts and runs for 30 seconds and stops! Am I right or wrong? Thanks again, Tom.
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Saturday, September 17th, 2016 AT 3:46 PM
Tiny
CARADIODOC
  • EXPERT
That is how they most commonly fail on all car brands. Here is the end of my earlier reply:

"To add to the insult, those sensors often fail by becoming heat-sensitive. One will fail after the engine has been running and commonly after a hot engine has been off for a few minutes. That eliminates natural air flow that helps to keep them cool. They will work again after they cool down, typically after an hour or so".
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Saturday, September 17th, 2016 AT 5:20 PM
Tiny
TOPDAD1947
  • MEMBER
So your saying I should change both? Or one at a time? And which one should I replace first? Thanks again, Tom.
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Saturday, September 17th, 2016 AT 6:21 PM
Tiny
KEN
  • ADMIN
Hey topD

I know its a little crazy but have you checked the engine oil and made sure there is gas in the tank? Both of these will make the engine shut down in thirty seconds. Here is a diagram of the circuit open relay location

Please let us know what you find so it will help others.

Best, Ken
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Saturday, September 17th, 2016 AT 11:57 PM
Tiny
TOPDAD1947
  • MEMBER
Yes! I have and your diagram of the circuit opening relay does not exist. I Disassembled the whole dash board looking for it. Right side kick panel no. Behind glove box not there either. Under the hood no. Behind radio no. Under drivers side fuse panel. I am frustrated as to what to check next? My wife loves this car and so do I. Do you have anymore thoughts? Would be greatly appreciated! Thanks, Tom.
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Sunday, September 18th, 2016 AT 12:15 AM
Tiny
KEN
  • ADMIN
Can you give me the manufacture date on from the sticker on the drivers door please, it could be a 1995 or 1997 then I can try to look it up that way.
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Sunday, September 18th, 2016 AT 10:27 AM
Tiny
TOPDAD1947
  • MEMBER
OK Ken I will get back to you with that info. Also there are two relays In the lower passenger kick panel. But they do not say circuit opening on them? Will you get you that information too? Thanks again, Ken.
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Sunday, September 18th, 2016 AT 10:54 AM
Tiny
TOPDAD1947
  • MEMBER
Yes I did that too! Thanks Ken, Tommy.
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Sunday, September 18th, 2016 AT 10:56 AM
Tiny
KEN
  • ADMIN
They will not say what they are on them. They are identified by location.
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Sunday, September 18th, 2016 AT 11:03 AM
Tiny
TOPDAD1947
  • MEMBER
OK Ken thanks again. Will do this as soon as possible. And get back to you! Tommy.
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Sunday, September 18th, 2016 AT 11:07 AM
Tiny
KEN
  • ADMIN
Sounds good Tommy :)
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Sunday, September 18th, 2016 AT 6:21 PM
Tiny
TOPDAD1947
  • MEMBER
OK Ken Looks Like You Got This Right! Manufactured On 01/97 The Two Relays Are One Denso Five Pin and On Bosch 4 Pin! Awaiting Your Reply? Tom.
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Sunday, September 18th, 2016 AT 6:33 PM
Tiny
CARADIODOC
  • EXPERT
I'm baaa-aack. Referring to some previous comments, on all fuel-injected cars, other than for one second when you turn on the ignition switch, the fuel pump will never run unless the engine is rotating, (cranking or running). If a fuel line is ruptured in a crash, the pump would dump raw gas on the ground creating a major fire hazard. Instead, the engine can't run without fuel pressure to the injectors, so it stalls. With a stalled engine there will be no signal pulses from the crankshaft position sensor or the camshaft position sensor. Lacking those pulses tells the Engine Computer the engine isn't running so it turns off the fuel pump by way of the fuel pump relay, fuel injection relay, automatic shutdown (ASD) relay, or in your case, "circuit opening relay". The names are different but the function is the same. The fuel pump gets turned off and stops dumping fuel on the ground.

Where checking the oil level comes in is some manufacturers have some engines that turn the fuel pump relay on by grounding its coil through a tap on the oil pressure switch or sending unit. A stalled engine has no oil pressure so the fuel pump gets turned off. Low oil level will, in a round-about way result in lower-than-normal oil pressure and that can result in a relay that turns off well before the low-oil warning light turns on. This goes way back to the early Chevy Chevettes that had carburetors and an electric fuel pump in the tank. I worked with a fellow who had one and had this problem on his way to work. We had never seen that before, but after some head-scratching on the side of the road, he added a quart of oil and made it to work. His engine was stalling about every two or three miles.

As I mentioned earlier, the fuel supply system is responsible for a very small percentage of crank / no-start problems as is the ignition system. It's the cam and crank sensors that cause most of the problems. We never replace one to "try it" except as a last resort. Doing so could inject another problem and a new variable. These sensors are listed on the live data screen on a scanner with some type of indication as to whether the signals are showing up during cranking. Chrysler, for example, lists theirs as "No" or "Present". To further complicate things, a diagnostic fault code can be set related to the missing signal for either sensor, but due to the long list of conditions that must be met to set a fault code, one is often not set in the short amount of time a stalled engine is coasting to a stop. Also, the list of conditions usually includes, "the signal is not monitored during the first five seconds of cranking" or something similar to that. That means without the scanner to view live data, you may not find this with a simple code reader. Even when a fault code has been set, if the battery is disconnected before the codes are read, they will be erased and may not set again from just cranking the engine.

Those two sensors are the first thing we think of when anyone mentions "stalls after running for... ", Or "stalls when hot", or "won't restart when warm until it cools down for an hour". The mistake the largest percentage of competent do-it-yourselfers make is getting hung up on the first thing they find missing, and that is fuel. Our first question is always, have you also checked for spark", because spark AND fuel are lost when a signal is missing from one of those sensors. That tells us whether you have a fuel supply problem, an ignition system problem, or the more common sensor problem that's common to both systems.

Your comment about "Circuit Opening Relay" not being printed on your relays made me chuckle. One of my best Electrical students made the comment that he could follow my drawings on the chalk board, but there were no red and blue chalk lines under the hood of the car, and the parts weren't so nicely labeled. Up till then I had never given that any thought as to why some people have trouble with electrical parts they may have never seen before. I forget that this applies to you and most other people too.
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Sunday, September 18th, 2016 AT 7:33 PM
Tiny
TOPDAD1947
  • MEMBER
Well Thanks For That Informative Brow Beating! :) :) But According To The Toyota Dealer In My Area And He Showed me The Relay By The Way! And Written On It Was U Guessed It Circuit Opening Relay! So I Guess They Fall Into Your Electrical Students Class! But Now I Will Get The #'s On That Relay And Try And Track It Down Or Test It With An Ohm Meter! Thanks Again Tom. P.S. If U GOOGLE 96/97 Circuit Opening Relay! You Will Be AMAZED HOW MANY THEY HAVE THAT SAY THAT ON THEM >>>
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Monday, September 19th, 2016 AT 1:00 PM

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