Attention EVO X owners: Potential Relay issue which may cause your car to run lean!
Aug 25, 2009, 04:14 PM
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Attention EVO X owners: Potential Relay issue which may cause your car to run lean!
Recently I have seen an event happening which I felt would be worth mentioning to those of you that own an EVO X. I may have found an issue that would affect the fuel system of the car and make the car run very lean, and possibly cause engine damage. The issue is related to the stock fuel pump voltage switching relay. The Evolution 8, 9 and now the 10 all have a relay which switches the fuel pump from low voltage to high voltage when certain conditions are met (full throttle, or boosted conditions).
The purpose of the relay switching the voltage is so that the fuel pump will last longer due to the reduced load it will see about 9 volts. When the car goes full throttle full battery voltage (13.5-14.5V) is needed for enough fuel flow even at the stock tune’s levels.
The issue that I have been seeing is that the relay will be stuck in the LOW position. Obviously you can see how this would be a major issue. I had it happen to me once here at AMS, I swapped it out the with Daytime Running Light relay and everything seemed to be fine, and I thought nothing of it. Recently though, on a tuning trip to Texas I had the same exact thing happen to me 2 more times. I would hop in a customer’s car and do a baseline pull to see where the car was at before making any changes, and it would be the 13’s and 14’s for air fuel ratio. After messing with the first car I was tuning a bit trying to figure it out, I remembered the issue that I had on the car back at the shop and I swapped the relays. Immediately the car was super rich when in full boost because of all the extra fuel I had added in at the lower pump voltage.
I thought that it was odd that it had happened twice, but then again the next day when I was out tuning cars it happened AGAIN! Again I swapped the relay and everything was all good. Later on that day I received a call from one of my customers saying that his DRL’s were staying on and he was asking me I knew any possible reason why…
.
So, in summation I would like to make it known that there may be a possible issue with some cars and their fuel pump relays. I think this may be the cause of several of the motor failures that have been noted around EVOM and may currently be the cause of other supposed engine failures due to weak parts.
What you should do:
If you have an EVO X with a wideband A/F gauge in it, just check your A/F ratio
If you have an EVOX without an A/F gauge in it, I would swap out the fuel pump relay with the DRL relay and see if there is an issue with your DRL’s staying on with the car off. I have had several cars where I swapped the relay out with the DRL’s and have had no further issue, however I believe that one relay was so far gone, that it actually kept the DRL’s on.
If you have an EVOX and are super paranoid about what may happen, I would get a volt meter and a buddy and pull up your rear seat and find the fuel pump positive wire. With the car running you should have about 9V, when the car is in boost you should have above 12V and there should be a clear point at which it switches.
If you are super duper paranoid and you don’t care about your warranty it may be a good idea to hot-wire your pump.
Here is the circuit:
This issue seems to be prevalent on cars with higher mileage on them.
The purpose of the relay switching the voltage is so that the fuel pump will last longer due to the reduced load it will see about 9 volts. When the car goes full throttle full battery voltage (13.5-14.5V) is needed for enough fuel flow even at the stock tune’s levels.
The issue that I have been seeing is that the relay will be stuck in the LOW position. Obviously you can see how this would be a major issue. I had it happen to me once here at AMS, I swapped it out the with Daytime Running Light relay and everything seemed to be fine, and I thought nothing of it. Recently though, on a tuning trip to Texas I had the same exact thing happen to me 2 more times. I would hop in a customer’s car and do a baseline pull to see where the car was at before making any changes, and it would be the 13’s and 14’s for air fuel ratio. After messing with the first car I was tuning a bit trying to figure it out, I remembered the issue that I had on the car back at the shop and I swapped the relays. Immediately the car was super rich when in full boost because of all the extra fuel I had added in at the lower pump voltage.
I thought that it was odd that it had happened twice, but then again the next day when I was out tuning cars it happened AGAIN! Again I swapped the relay and everything was all good. Later on that day I received a call from one of my customers saying that his DRL’s were staying on and he was asking me I knew any possible reason why…
.So, in summation I would like to make it known that there may be a possible issue with some cars and their fuel pump relays. I think this may be the cause of several of the motor failures that have been noted around EVOM and may currently be the cause of other supposed engine failures due to weak parts.
What you should do:
If you have an EVO X with a wideband A/F gauge in it, just check your A/F ratio
If you have an EVOX without an A/F gauge in it, I would swap out the fuel pump relay with the DRL relay and see if there is an issue with your DRL’s staying on with the car off. I have had several cars where I swapped the relay out with the DRL’s and have had no further issue, however I believe that one relay was so far gone, that it actually kept the DRL’s on.
If you have an EVOX and are super paranoid about what may happen, I would get a volt meter and a buddy and pull up your rear seat and find the fuel pump positive wire. With the car running you should have about 9V, when the car is in boost you should have above 12V and there should be a clear point at which it switches.
If you are super duper paranoid and you don’t care about your warranty it may be a good idea to hot-wire your pump.
Here is the circuit:
This issue seems to be prevalent on cars with higher mileage on them.
Aug 25, 2009, 08:09 PM
#3
I would say go DSM style and just use the fuel pump power wire to turn on a relay that would power the fuel pump directly from the battery. I mean the battery is right there!
Aug 25, 2009, 09:03 PM
#4
Your title says Evo x but then you say "The Evolution 8, 9 and now the 10 all have a relay which switches the fuel pump from low voltage to high voltage when certain conditions are met". So are you saying all USA Evos are at risk or just the Evo 10?
Aug 25, 2009, 10:02 PM
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We had the same issue over here on a couple of cars as well, cars with larger aftermarket fuel pumps are more vulnerable to relay failures.
He said they all have a relay which switches from low to high, but the 10 has issues with its relay.
He said they all have a relay which switches from low to high, but the 10 has issues with its relay.
Aug 25, 2009, 11:12 PM
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The easies test is to swap the fuel pump relay #1 with the high beam relay and see if the high beams illuminate, or stay illuminated. If they don't turn on at all, complete relay failure. If they turn on momentarily, partiallly failing.
Here is the test right out of the shop manual
Here is the test right out of the shop manual
I then refered to the Mitsu Shop Manual for further guidence in diagnosis. I used the following step to verify the operation of the High Load fuel pump voltage state
Fuel Pump Relay is located here
This was the results of my bench test on the fuel pump relay, a bad relay. The resistince was OL, which on this meter means out of limits and that means the circuit is open
Just to verify the test that I was performing, I tested the horn relay, it was good. Resistance measured 0.0
That is all I have for now. I am going to swap the horn relay with the fuel pump relay since it is the same exact part as temporary fix, and I will replace the horn relay at a later time.
I will try and get some more log data with Naji very soon and post the results here with the relay replaced
Fuel Pump Relay is located here
This was the results of my bench test on the fuel pump relay, a bad relay. The resistince was OL, which on this meter means out of limits and that means the circuit is open
Just to verify the test that I was performing, I tested the horn relay, it was good. Resistance measured 0.0
That is all I have for now. I am going to swap the horn relay with the fuel pump relay since it is the same exact part as temporary fix, and I will replace the horn relay at a later time.
I will try and get some more log data with Naji very soon and post the results here with the relay replaced
Last edited by Spunkysandoval; Aug 25, 2009 at 11:18 PM.
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Aug 27, 2009, 10:09 AM
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Posible solucion/upgrade -> Boost-A-Pump
It could also solve the problem with output variations, depending on lights been on, or the A/C, or the stereo, etc etc...
Originally Posted by How it Works
While dyno and street testing, our On Board Data Logger told us that fuel flow was less at night when the lights, stereo etc. were on. The voltage to the pump was varying between 12 and 13.5 volts and fuel was being reduced up to 15%. Further testing in our Fuel Flow Lab indicated that by elevating the voltage to the pump we could safely increase fuel capacity by as much as 50%. The Kenne Bell BOOST-A-PUMP™ does just that - and it automatically maintains the pre-set voltage or % increase with as little as 10 volts at the battery.
The Kenne Bell BOOST-A-PUMP™ is fully adjustable from 1% to 50% with the mere turn of a dial, so pump output can be varied to match your engine's needs. No longer are you "locked in" to a fixed pump capacity and/or pressure. It activates ONLY at full throttle (naturally aspirated) or at 3 psi (turbo or supercharged). And it acts as a voltage regulator by compensating for any and all system voltage fluctuations.
Aug 27, 2009, 02:19 PM
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how do you test it if you don't have a a/f gauge installed? i'm staring at the diagram but it doesn't really make much sense to me.
should i be concerned? my X only has 1400 miles on it.
should i be concerned? my X only has 1400 miles on it.
Aug 27, 2009, 03:43 PM
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do the easy test take out your fuel pump relay trade/switch it with the highlight relay.
Next switch on the highlights.
Suposively if your highlight don't go on or go off after a few seconds then you have a bad relay.
someones more then welcome to correct me but its what i got from this thread.
I tried it and doesn't seem to be my problem yet
Next switch on the highlights.
Suposively if your highlight don't go on or go off after a few seconds then you have a bad relay.
someones more then welcome to correct me but its what i got from this thread.
I tried it and doesn't seem to be my problem yet
Aug 28, 2009, 11:54 AM
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http://www.powerstream.com/dc2.htm
Another good option IMHO at less than $200
They have variable input, 9 VDC to 14 VDC and will not turn off during car starting if the voltage stays above 6 volts. It also has a GOOD SIDE-EFFECT, your pump will flow more because of the added energy.
Another good option IMHO at less than $200
These are Boost Converters. which put out 13.8 volts with an input voltage of 12V nominal. (10-15V) We stock other output voltages in the PST-SR700 package, see our web page for options. We also stock an adjustable version of the SR700 that runs from 15 to 24 volts. This adjustable dc/dc converter (PST-SR700-adjustable) has a front panel knob to adjust the voltage, but is otherwise identical to the fixed voltage converters.
Mar 22, 2010, 11:42 AM
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Some of us rely on you tuner guys with our lives. Can I bring it in sometime and you explain it to me or help me out with this? I am paranoid cause I have 22k on it with maybe 10 of it with the tune already. People killing their motors on mild tunes...what the heck is this ? * I think I have the black fuel relay still in there that I just realized has been causing some people issues. Is it safe to swap for the new one with a tune?
* I think I have the black fuel relay still in there that I just realized has been causing some people issues. Is it safe to swap for the new one with a tune?
Last edited by love9sick; Mar 22, 2010 at 02:05 PM.
Mar 23, 2010, 10:23 AM
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Some of us rely on you tuner guys with our lives. Can I bring it in sometime and you explain it to me or help me out with this? I am paranoid cause I have 22k on it with maybe 10 of it with the tune already. People killing their motors on mild tunes...what the heck is this ? * I think I have the black fuel relay still in there that I just realized has been causing some people issues. Is it safe to swap for the new one with a tune?
* I think I have the black fuel relay still in there that I just realized has been causing some people issues. Is it safe to swap for the new one with a tune?