GorgeSuby Posted January 26, 2021 Share Posted January 26, 2021 Hi, Guys I have been dealing with an intermittent & worsening cold start issue with my EJ25 Legacy OB... So far I have done a tune-up & replaced some sensors: Knock, Coolant temp, Crank position. It was running well & CEl stayed off but last cold snap it would not fire again & it has been getting worse. A few days ago I noticed that when it didn't start, I could not hear the fuel pump kick on, but after awhile when everything warmed up it would kick on & start priming again. I thought I figured it out when I was getting voltage at the pump connector but no pump sound. However after pulling the pump & connecting it directly to battery voltage, it fires up & runs... when testing voltage directly at the pump connector it seems to briefly spike up to 12v then nothing. Is that normal? What do you think my issue could be? Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 26, 2021 Share Posted January 26, 2021 Yes the fuel pump is only powered for a short time when you first turn the key on. Once the engine is running it's always powered. Sometime your meter may lie to you. If you have no load on the circuit you can read voltage but still not have what you need. You Tube search Load Pro. You might want to try the relay under the dash. If you can back probe the connector and leave it hooked to the pump that would also give you a better voltage reading. Check the circuit under load! When this happens you could also pour a little gas in the intake. If it fires you have confirmed it's a fuel issue. Gas water Free? 2 Quote Link to comment Share on other sites More sharing options...
GorgeSuby Posted January 26, 2021 Author Share Posted January 26, 2021 (edited) Thanks, Don't think it would be water... after I pulled the pump & tested it direct to battery, I hooked it back up to the connector & still no hum.... will try the back probing. Thought of relay too but after searching the forum quite a bit, consensus seemed to be they rarely fail & are hard to get to... still could be it though... Edited January 26, 2021 by GorgeSuby Quote Link to comment Share on other sites More sharing options...
Rampage Posted January 26, 2021 Share Posted January 26, 2021 Don't forget the ground for the fuel pump. It needs both hot and ground to run. It will be the other big wire on the connector at the pump. If you see voltage on that ground wire when the pump is supposed to run, then the other end of it is not making good contact to body ground. When you have the pump assy. out the 2 wires from the pump have a connector that plugs into the bottom side of the big connector. I found one of those pins burned off one time. The ECU controls the relay for the fuel pump. If the engine is not cranking or running it turns off the fuel pump after a few seconds. The Load Pro that lmdew mentioned can be a useful tool. I don't have one. It can apply a half amp load to a 12v circuit which can be very helpful at times but not always. Remove the panel under the steering wheel and lay it on the floor. Look for two green (test) connectors. Plug them together and turn the IGN SW to ON. The ECU will cycle the fuel pump, relays, solenoids and the radiator fans on and off. The cycle will repeat until you turn the key off. Very helpful to see if those things are working. When you hear the fans go off the fuel pump should cycle on and off. Remember to unplug them. 1 Quote Link to comment Share on other sites More sharing options...
GorgeSuby Posted January 27, 2021 Author Share Posted January 27, 2021 Thanks Rampage. Maybe I will try plugging it back in & cycling the power with ground on connector grounded to frame... will look into those test connectors too. Quote Link to comment Share on other sites More sharing options...
GorgeSuby Posted January 29, 2021 Author Share Posted January 29, 2021 (edited) So followed Rampage's advice & used the test connectors. (Thanks!) After verifying voltage at the connectors, I plugged the pump back in. The pump would cycle with the fans but not every cycle? It seemed some cycles it would run every pulse whereas sometimes it would just click faintly for a couple cycles then run again... So what do you think? Pump failing to start intermittently due to: 1) Bad pump? ... this is about a 3 year old aftermarket - Carter pump. 2) Low amperage? Seems to be getting the voltage but maybe low amps? 3 )Intermittent bad ground? Not an electrical genius, so any help appreciated! Edited January 29, 2021 by GorgeSuby Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 30, 2021 Share Posted January 30, 2021 I'd start with the relay. Easy to swap, used ones OK. I've had the same problem more than once. Quote Link to comment Share on other sites More sharing options...
Rampage Posted January 30, 2021 Share Posted January 30, 2021 2 hours ago, GorgeSuby said: 1) Bad pump? ... this is about a 3 year old aftermarket - Carter pump. 3 years on a Carter pump is pretty good. With our 95 Legacy the Carter 2in. and 1.5in. diameter pump would quit in 11 months, just short of the 1 year warranty. I replaced it several times under warranty, then a Denso pump showed up in the Carter box. That one lasted a long time. If I remember right, the OE was a Denso. The next time you hook up the green test connectors and the pump does not want to start, check the voltage on the positive wire to the pump with the connector still plugged in. If the voltage is low, the relay is the problem. If the voltage is almost 12v, tap the oval mounting plate with a small hammer. If the pump starts running the pump is bad. Some times they will not start when the pressure is still high. I think it has to do with the contact of the brushes with the commutator on the armature. 1 Quote Link to comment Share on other sites More sharing options...
GorgeSuby Posted January 30, 2021 Author Share Posted January 30, 2021 So I was able to back probe the connector during the diagnostic cycle. When the pump fails to start on the regular cycle the voltage is low - like less than 1v so looks like relay after all. 1 Quote Link to comment Share on other sites More sharing options...
Rampage Posted January 30, 2021 Share Posted January 30, 2021 Less than 1 volt does sound like the relay. Now for the fun part, getting to the relay. I have changed it and the main relay. The fuel pump relay is the round one and snaps into a metal U shaped clip on the bracket. The FSM shows a picture of them and the bracket holding them. It also lists what to remove to get to them. Disconnect the battery first. Good luck. Quote Link to comment Share on other sites More sharing options...
GorgeSuby Posted January 31, 2021 Author Share Posted January 31, 2021 Replaced the relay(what a pain..) put everything back together - so far so good ... diagnostic cycle fires it every time. Starts up every time so far. Frosty morning tomorrow will be the moment of truth. 1 Quote Link to comment Share on other sites More sharing options...
Rampage Posted January 31, 2021 Share Posted January 31, 2021 Very good !!! You made it through that ordeal. Our cars are RHD, so the relay is on the right side and I have to work left handed under the dash. Agreed, what a pain. Our 95 has 473+k miles on it and still the original fuel pump relay. I had to change the main relay in our 97 close to 300k. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.