SuperBonBon

I've been through the forums and can't find anything quite like the problem I have.....

The 4Runner starts just fine - every time. However, it only runs for a second or two, and then dies. It will then start again just fine, run for a second or two, and then die......over and over and over.

While checking/testing a few connections, I drove it around the block, and it died again 1/2 a block from home. My buddy was with me, and after trying a few things, he suggested holding the key in the "start" position to see what would happen. The truck continued to run (with the starter motor running, too...) so we drove it back while I held the key in the "start" position.

Since I was out of town and not able to really tear things apart and/or run around buying parts, I came upon the idea of putting a jumper in near the ignition that would simulate having the key in the "start" postion (when the key was in the normal "run" position. I also wired a simple on-off switch to the lead wire on the starter motor so that it wouldn't be on the whole time (and obviously burn out and/or self-destruct) I drove the truck like that for 3 hours (to get it home), and it ran perfectly (but seemed to use more fuel).

I've since picked up a replacement key ignition wire harness. I plugged it in today, and the truck ran perfectly. I drove it around town for about 15 minutes to test it, and it continued to run perfectly, so I thought I had the problem solved. Then I brought it home and put it back in the heated garage where I was working on it, so that I could replace all the dash components I had removed. Before doing that, I turned the truck on and off at least a dozen times to "stress test" it - and it continued to work normally.

Then, after replacing the panels, I started it up....and the old problem returned. I then went under the hood, looking for possible sources (checking connectors, vacuum hoses, etc.). Along with plugging and unplugging all the fuses located under the hood, I checked a couple of connections and wiggled a few wires. Tried starting it again - and it started right up and ran perfectly.

I left the truck alone, and decided to check this site for possible answers. When trying the truck again - the original problem returned.

So obviously the problem is intermittent. I first saw the problem 2 weeks ago - the same symptoms, but after about 30 attempts the truck started and then ran normally during the past 2 week period. On the way out of town this weekend, the problem returned. After letting the truck sit for a 1/2 hour, it started again and ran fine the last 150 miles to my destination. Once arriving there, the truck died 95% of the time, and ran 5% of the time. After installing the "jumper", the truck ran 100% of the time (the 3 hours spent getting the truck home).

Any ideas?

SuperBonBon

Update:

I believe I've found the problem. There is a relay located in the dash directly above the ECU. In experimenting with that relay it seems to have solved the problem.

I'll replace it tomorrow and see if it solves the problem permanently. If it does, I'll post the results here in order to help out "the next guy"!

leiniesred

fuel pump relay gets tripped ON in START or if the MAF flapper is open and the key is on RUN. Check the flapper for sticking and the intake trunking for a major leak.

You are on the right track. either the relay, or the signal to the relay.

SuperBonBon

Hi leiniesred,

I changed the relay today....same problem. So I looked over the original relay (the one that I had out of the plastic casing) to see if I could analyze how it functions. I rconcluded that there were 3 different leads into the relay, and 1 lead out, so I realized that another signal had to be coming from somewhere.

I got on this forum and other sites, and noticed a lot of discussion about the MAF and how it controls the relay in question after startup. The '86 and others near the same generation of truck has a VAFM, but I figured it functioned nearly the same way and could cause the same problem, so I found specifications for it and began testing it. It checked out OK, including the all-important lead that feeds back to the relay. Then I went to see if power was getting to the VAFM, and........VOILA!!!!

One of the female clips inside the housing that connects to the VAFM was slightly disconnected/pushed back into the housing. I took off the rubber seal, and it "popped" right back into place. Plugged in the new relay and everything else, and instant success! Runs just like new again!

Hope this helps someone else!