Fuel Pump doesn't kick in when hot?

Okay I know there is probably something around here somewhere that will solve my problem but I can’t find it and my Haynes manual doesn’t seem to be giving me an anwser to my problem so here goes. On a hot day my car cranks but won’t start for a while. Also happens more so after I’ve been driving and parked somewhere only to come back to it and it won’t start. I’ve noticed that I can’t hear the fuel pump kick in when it’s not starting but I’ve been told if there is a problem with the fuel pump it will never start. It’ll either work or it won’t. I’ve swapped the main relay with the one in my other teg and the problem is still there. I’ve been having this problem for a good two years now and it’s really starting to aggrivate me. I’ve also put in a new fuel filter and I have a new fuel pump but I was planning on putting it into my other teg and those things are kinda pricy so I don’t wanna drop a new one in it unless I have to. The car is a '92 RS with 286,xxx kms on it. Manual transmission with B&M short shifter and only mods are a CAI and 2 1/4 cat back exhaust. If someone could give me a hand or point me to a thread that has the anwser I’m looking for that would be great.

odds are extremely good its still your MFR.

if you just swapped it with another old unit then they probably both have the same issue.

if you dont want to spend the $75 for a new one… take the old one apart and look for fine rings (cracks) around some of the solder joints. those are the issue.

re-solder them and you should be good to go.

ill bet if you check the other MFR you will see they both have the same rings/cracks

Okay I’ll try opening it up on Thursday and see what kinda shape it’s in. After wednesday I’ve got two and a half weeks holidays if I screw the thing up and have to order a new one at least I won’t be needing the car. lol

Okay I desided not too wait. I took the relay out and opened it up. Nothing really looked cracked or anything but the soder did have little swirl marks in it that just looked like a discoloring more then cracking. Anyways I just put a little dab of soder on each of the existing ones and reinstalled it and had the same problems. The car stalled out a couple of times just after starting but I’ve had that problem with it from time to time as well but I’m pretty sure it’s the same problem. Personally I’m not the greatest with soder though so on monday I’ll see if I can pick up another one after work and I’ll keep my fingers cross that it works. Although if you could get back to me sooner and let me know if the swirl marks sound like the problem before I go out and pick up a new one that would be great.

hey man i got one for 25 shipped just let me know

test the ignitor and ignition coil to see if within specs.

spikeymike, if the problem was either the ignitor or ignition coil wouldn’t I still be able to hear the fuel pump? I’ll probably still check them but it sounds like an odd solution when I’m pretty confident it’s the fuel pump that doesn’t wanna turn on when it’s hot. I think the Haynes manual mentioned something about a faulty oil pressure switch won’t let your fuel pump turn on either. Is this a posible problem or would my car not want to start at all. I was also thinking maybe O2 sensor or anything else along that line that might give the ECU a reason to not let the car start? Just some idea’s I’ve been tossing around in my head.

there are many things that could cause a car not to start when its hot.

a bad ignition coil or ignitor can cause a car to start and die later in hot weather. if you want to focus on one particular part when there are many other related parts that could cause the problem, be my guest.

a bad o2 sensor would not cause your car to die or not start.

No, no. The car doesn’t die when it’s hot and I’m driving it. Sometimes it stalls out just after starting but once it’s running it stays running. It’s like as soon as it fires up it sputters and dies.

MFR MFR Main Fuel Relay MFR MFR

I have the exact same problem. When it is hot it will start then sputter a few times and die. I am almost certain that it is a “cold solder joint” or something wrong with the “MFR” b/c if I bang on the dash where the MFR is bolted (just under the change holder to the left below the steering wheel) while simultaneously turning the key the engine starts up and does just fine.(this really does work and I am sure others have done the same thing) I have the replacement MFR that I bought from the dealership but, just getting every last drop out of this one.

Ya I plan to pick up a brand new relay on thursday when I go on holidays but I know I tried shaking mine once when it was reluctant to start and it didn’t seem to help. Didn’t really bang on it or anything just shook it. Although I’m still leaning towards it being the problem. Keeping my fingers crossed. lol

b/c if I bang on the dash where the MFR is bolted (just under the change holder to the left below the steering wheel) while simultaneously turning the key the engine starts up and does just fine.(this really does work and I am sure others have done the same thing)

this works? everytime for you? damm i usually cry, roll up a dub, and walk to the train station. and come back later at night to get my car… but im going try that next time.(untill i get another MFR)

ive tried alot of weird shit to get it going, like instant cold spray from the first aid kit, just emptied the can under the dash, but that rarely works. haa

Bang the MFR

It really does work man…I happens almost every time the temperature outside exceeds 80 degrees or so. I should just change it out but, I am using the old one for all its worth.

i tried banging on the dash near the MFR. but i couldnt get it too go. but i did finnaly sit down and add new solder to the MFR and its working pretty good soo far. wish i did it a year ago.

Im having this same problem. I changed out the MFR and it seemed to work for a few days…though I didn’t really pay much attention to the outside temp. Then it stopped working. So, I changed the fuel filter. Again, it worked for acouple days but quit again.

When it is below about 75 outside it starts up and runs like a champ. However, when it is hot out it will not start. I usually just get a ride home from work and then come back at about 8pm and it fires right up. WTF.

I bought a fuel pump and am planning on installing it this Saturday…what a pain. I know for a fact that the line is getting no pressure when the car has been sitting in the sun because i loosened the bleeder bolt on the Fuel filter and nothing came out. Also, prior to doing that, I opend the gas tank and it didn’t make the sound of depressureizing.

Should I try something else before the pump? How could my pump be doing this. I use midgrad Chevron everytime and have for the last two years. Could it be that the line is being clogged with crap?

P.S. If the pump doesn’t work I may be running the car into a pole. :slight_smile:

did you install a brand new MFR or used one. sounds like its the MFR. i dont think heat should affect the fuel pump. if it is a used one maybe re-solder the MFR.

i did alot of coming back in the evening to get my car… haa.

mine does this but after sitting for the key on for a bit it turns on aftre a few tries.

The MFR was brand new. I know it’s a newb question but can you tell me where I need to solder? Pics perhaps :slight_smile:

if the MFR was brand new, then that probaly wasnt your problem(athough it sure sounded like it was) . now you gotta keep trouble shooting. fuel injection? ignitor coil, i dunno dude.

These may help you
How it works
How to fix

If you do a search you may also find more info that will help you.