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420A 95 NT died under WOT and now won't start, how to diagnose and locations

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langelg6

Proven Member
52
13
Nov 4, 2019
Hammond, Indiana
hello I have a 95 talon 420a FWD N/T and manual transmission

car pretty much died under WOT and wouldn't start. no mechanical whirring of the fuel pump when key is on run position and pulled a fuel line at the fuel rail, started it and was bone dry. before I go and drop $100 on a wally fuel pump. I would like to know how to diagnose the relays associated with the fuel pump

I have been confused as to which is my fuel pump relay.. I think its the black box on the firewall next to a grey relay but I have been reading that the fuel pump relay is on the passenger seat next to their leg... Once I track down these relays how would I test for power or what is it I would exactly be doing to diagnose?? sorry if I sound like an idiot.
 
That's for the turbo 4g63. The 420A is P0335 (no crankshaft reference signal at PCM) or P1391 (intermittent loss of CMP or CKP).

I haven't got home to check.. so the exact code number I won't have any clue til the morning... But I remember it forsure said "intermittent loss of cmp or cpk"

While I was gone dad got in my car and cranked it over, the tachometer stayed on 0 and didn't buge while he was cranking the car

anyone with a N/T eclipse or talon with a 5speed, would you kindly confirm if the tach is supposed to jump to 200-300 rpm during starting
 
I cant ever remember seeing that when I start mine up.

oh boy LOL, I can't quite recall myself tbh but I read up somewhere that it should during cranking if the crank sensor is in working order.
 
My tach doesn't move until the engine starts to combust

hmm interesting. all I have to rely on my crank sensor theory is sypmtoms and engine code.

don't know if it relates but when first cold starting my rpms stay at 1000 rpm but slowly makes its way up to 1500rpm.. If I take off without letting it hit 1500rpm it will 100% always die when approaching a stop sign/light and keep dying until warmed up.... My pcv cracked slightly and raised rpms to 2000-2500 some how prevented this when I would leave when cold out.. what are the negatives of leaving pcv valve like that?
 
Replace your pcv, sounds like there is either an idle issue or vacuum leak when it's running. Also the dying at a stop sign/light before letting it get to 1500 (basically letting the engine warm up) sounds like faulty IAC or a bad coolant temp sensor.

You're throwing out a lot of info though, get the codes pulled and figure out the no start then go from there. Cant diagnose other issues if it wont start up yet haha. Keep posting and I can try to help you out the best I can. I got lemon with my 2gnt but I made it work and figured everything out either on my own or with help from this forum.

Respect to all the guys and gals on here cause the DSM life ain't easy!
 
Replace your pcv, sounds like there is either an idle issue or vacuum leak when it's running. Also the dying at a stop sign/light before letting it get to 1500 (basically letting the engine warm up) sounds like faulty IAC or a bad coolant temp sensor.

You're throwing out a lot of info though, get the codes pulled and figure out the no start then go from there. Cant diagnose other issues if it wont start up yet haha. Keep posting and I can try to help you out the best I can. I got lemon with my 2gnt but I made it work and figured everything out either on my own or with help from this forum.

Respect to all the guys and gals on here cause the DSM life ain't easy!


well let me say you sure know what you are talking about... The only other codes I pulled were for ECT, IAC and some weird code about secondary pulse air system injection (the ect I knew about the connector has been cut off since ive owned the car) and the iac I think is because pcv is broken)

I suspected a crank sensor when the car first started stalling but never tested. and to my knowledge this secondary air system is some piping to the airbox (which is non existent in the tallywhacker) from the header.
 
It's a 95? I'm only guessing here but that secondary air pulsing you're referring to might be the fuel pressure regulator hose. On the 95-96 models the FPR is mounted on the fuel rail and the line goes directly to the intake. On 97-99 the FPR is located on the firewall and the hose runs down behind the engine. Not sure what secondary air pulsing injection is referring to off the top of my head.

Also your pcv purely mechanical and wont cause any codes other than a possible lean condition from having a vacuum leak. That hose line needs to be solid and definitely replace the part itself if it has a crack.

Keep in mind these cars are all over 20 years old and most hoses and or belts even if replaced are probably worn/cracked or in the process of doing so. I know you've talked about throwing a turbo on there, do you know when the timing belt was done? If not you should add that to the list, we have interference engines. So if that fails you will be in the market for a new head and possibly pistons.
 
It's a 95? I'm only guessing here but that secondary air pulsing you're referring to might be the fuel pressure regulator hose. On the 95-96 models the FPR is mounted on the fuel rail and the line goes directly to the intake. On 97-99 the FPR is located on the firewall and the hose runs down behind the engine. Not sure what secondary air pulsing injection is referring to off the top of my head.

Also your pcv purely mechanical and wont cause any codes other than a possible lean condition from having a vacuum leak. That hose line needs to be solid and definitely replace the part itself if it has a crack.

Keep in mind these cars are all over 20 years old and most hoses and or belts even if replaced are probably worn/cracked or in the process of doing so. I know you've talked about throwing a turbo on there, do you know when the timing belt was done? If not you should add that to the list, we have interference engines. So if that fails you will be in the market for a new head and possibly pistons.


so more diagnosis this time with a full system Ilink 400 scan tool.. it's not a full on dealership scanner but it is pretty close

so my findings are pretty interesting... My coolant temperature on a cold engine is 260 degrees fahrenheit!!!

I do have a code for tps sensor..... on my scan tool it states 12% throttle while NOT touching the accelerator and moves up to 77% tps on wide open throttle

while cranking ive noticed a severe loss in cranking power but my battery voltage is fine lights come on bright I hooked up a jump from another vehicle so I can test rpms.... during cranking it wouldn't register on my scan tool as other tests did. RPMs stayed on 0 while cranking on my diagnostic tool
 
also the battery is fairly new. I purchased brand new at o reileys back in december
 
Okay I would recommend an NTK brand tps because they make good products. Lucky for you the things that are bad are still available. Your throttle should read 11-12% at idle, I get the same reading on my scan tool. Something is clearly faulty with your coolant temp sensor if you're reading ECT of 260 and it's a cold engine. Your ECT shouldn't go above 210 during normal operations. Since you have a 95 make sure the connector you get is the oval kind not the square one (square connector is for 97+) unless you want to do some rewiring. NTK also makes a coolant sensor. Not saying you need to go with NTK but they are quality IMHO.

Also I made this mistake when installing my coolant sensor. It is has TAPERED threading so you WILL crack that housing bolted to the block if you aren't careful and screw the sensor in too much, and if you dont remove your upper radiator hose for removal/installation it will crack the sensor and will still work but the housing for the electric connection will be compromised and corrosion can occur. If the sensor you get doesnt have plumbing tape around the threads put some on yourself.

TPS is not related to the IAC valve. Your IAC is only in an open position mechanically when below 2k rpm, it should fully close that air pathway off when above that because it isnt needed for a more open throttle to control the rpm.
 
Oh yeah and that housing for the ECT sensor and your thermostat isnt available anywhere I could find, I had to get lucky and find it at a junk yard, so be gentle when installing.


Hmm is it possible that 2 codes just delete themsevles. the IAC code - P0505 and Crank code P01391 just disappeared on their own but stil no start
 
They are probably still there, it's possible the ecu lost connection and reset the codes. I've had that happen when I had to fix my positive cable and forgot to scre those little screws in all the way like an idiot. Ecu just randomly kept resetting. I'm lucky it didnt short anything.
 
They are probably still there, it's possible the ecu lost connection and reset the codes. I've had that happen when I had to fix my positive cable and forgot to scre those little screws in all the way like an idiot. Ecu just randomly kept resetting. I'm lucky it didnt short anything.


Here is where im at. I replaced the crank sensor, jumped the car and ran perfectly fine for 12 hours of going around town but crapped out again on my way home, same symptoms as before.. I figured bad connection so I replaced the connector and pig tail and still nothing

The CKP sensor I purchased was a $25 ebay one even then I doubt a cheap part would crap out 12 hours after arriving on my doorstep

I do believe that the engine got too hot and might have did something with the crank sensor but after 2 days it should still start.. When I went to change out the pig tail the new CKP just didn't seem right. the metal cylinder that inserts into the engine was able to rotate freely I don't remember if it naturally or the new ckp sensor got messed
 
If the engine overheated then it can certainly mess sensors up, the 420a engine gets pretty hot during normal operations. I wouldn't personally ever buy a cheap ebay sensor especially not a CKP sensor. If it was working after the fix then suddenly stopped I and it did happen to be the cheap part go get a brand new sensor from rock auto. Rock auto is great for these cars since parts are hard to come by.
 
If the engine overheated then it can certainly mess sensors up, the 420a engine gets pretty hot during normal operations. I wouldn't personally ever buy a cheap ebay sensor especially not a CKP sensor. If it was working after the fix then suddenly stopped I and it did happen to be the cheap part go get a brand new sensor from rock auto. Rock auto is great for these cars since parts are hard to come by.


Gonna test with multimeter on signal wire. while hand rotating the crank
 
Hi @609DSM
I was following this thread due to an issue with my 1995 gs . It shutdown while idle, but if I'm running everything is ok.
May I ask you for a photo of the part number of your Fuel pump relay and ASD relay? I'll try to replace those relays and see what happens.
 
You
hello I have a 95 talon 420a FWD N/T and manual transmission

car pretty much died under WOT and wouldn't start. no mechanical whirring of the fuel pump when key is on run position and pulled a fuel line at the fuel rail, started it and was bone dry. before I go and drop $100 on a wally fuel pump. I would like to know how to diagnose the relays associated with the fuel pump

I have been confused as to which is my fuel pump relay.. I think its the black box on the firewall next to a grey relay but I have been reading that the fuel pump relay is on the passenger seat next to their leg... Once I track down these relays how would I test for power or what is it I would exactly be doing to diagnose?? sorry if I sound like an idiot.
You don't sound like an idiot.
you're correct that the fuel relay is in the engine bay on the fire wall on the driver side. There's three relays typically, fuel relay is the middle one.
The same thing happened to me once on the track, last session of the day and I'm ripping it up when car just turns off. First thought was fuel pump or fuel relay. Actual cause was crank angle sensor, it was an easy fix after all.
to learn to check relays look it up on YouTube, much easier than anyone writing it down on a reply plus you get great visuals. I've used videos to check relays many times because I can't memorize the values LOL. Good luck with your problem no doubt you will get it up and running in no time.
 
The temperature sensors on our cars are thermistors: resistors that start high and go to a lower resistance as they heat up. Typically they'll be around 2000=3000 ohms at room temperature and you can check that with a multimeter. At any normal engine operating temperature they'll be a few hundred ohms -- maybe 500? I don't remember exactly.

If the ECU thinks the engine is at 260F (overheated!) at best the mixture is going to be far too lean. I don't know if there might be some logic to prevent starting an overheated engine.

Temperature stuff is complicated: There's more than one sensor for temp and I can't keep straight which one does which jobs but if the ECU says '260F' then for sure there are going to be things wrong.

That 260 sounds like a shorted sensor and I wonder if it could be an interment short in the wiring rather than the sensor itself?
 
on a 420a,
the ASD relay will be the one wtih a gray plug
the fuel pump will have a black plug
and if you have an AT, the EATX relay is the one with a white plug.


If the ECT sensor was shorted the ecu will activate a fail safe and run using the default coolant temp of 114F

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If the sensor isn't reading correctly because of higher resistance in the wire or the sensor,
the main issue is overheating.
It could only be off by 10-20 degrees which won't look to much different on the gauge but it cause the fans to come on at a higher temp than they should.
 
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