ashtsi

First things first. I've got a 90 4runner with a manual trans and the v6.
It's got spark and is getting fuel, but the dang thing just wont fire up. I go to start it and it just cranks and cranks and cranks. My best guess was that it's not getting a injector pulse. I looked through the book and figured it could either be the mas air flow sensor or the ecu. I got my hands on a new ecu, installed it tonight but it still wont fire.

The strange thing is that it will occasionally fire. Not often, but once in a great while it will fire. It has a mind of it's own! I will think i fixed it turn it off and start it again, it will fire so i button it up get it ready to take on a test drive and then it wont fire again.. back to square 1. At this point im out of ideas, and i just wanted to see if theres something im over looking before i go and replace the MAS.

Thanks,
Ash

thook

Oh man, don't go throwing parts at it. That gets expensive. If you learn first how to start testing and troubleshooting, it'll save you a lot of money. Hopefully you're atleast somewhat mechanically inclined?

At the times it won't fire up, have you noticed if the CEL is coming on solid when you turn the key over? I don't mean flashing any codes. Just coming on solid. It should always come on solid, with no flashes, when you turn the key to ignition letting you know that the ECU is powering up.

ashtsi

Sometimes it's on sometimes it's not. It's got some lame Aftermanket alarm. Clifford Arrow III. I tried taking bypassing it, and to the best of my knowledge succeeded. When it was disconnected the CEL was on solid when i would try to start it. I'm not sure if it stayed solid while cranking over, but i know it came on. When disconnecting it didn't work i hooked it back up and the CEL went off. I'll make better note tomorrow when i mess with it again.

Any idea what could be going on?

Thanks,
Ash

seanmearse

You said it has spark, has fuel. But, is the fuel pressure sufficient enough to make it run? Is the door on the VAFM opening smoothly (right above the air filter, upper part of the housing)?

4x4runr

Check the igniter connections next to the coil

thook

I don't know anything about alarm systems, except they can be annoying. Especially sitting in a parking lot and the owner is nowhere to be found. I have heard of people having problems with those systems, though.

Anyway, if the CEL always come on when this happens, that's atleast a good starting point. But, do make sure. If so, then connections are a good place to start inspecting. Sometimes that's all it is.....a loose/intermittent connection. Make sure the battery connections are good with no corrosion or loose fittings, make sure all the grounds are good from the battery to the block, to the fuse box, to all electrical components, no cracking wires at the connectors, no broken connectors, no loose or cracking vacuum lines, etc.

ashtsi

I haven't checked fuel pressure, but i did just replace the fuel pump and filter. I'm not sure how the VAFM door is opening, but i will make sure to check this evening when i go down to the shop to tinker with it.

ashtsi

Well when i put the new ecu in i disconnected the battery so the CEL isn't on anymore. with it not starting, how long should it take for it to come on again if at all? Do i just have to sit there and try cranking it over and over until the ecu figured out there's a problem and turns the CEL on?

So when you say check wires, do you mean basically the whole engine wire harness? Seems like alot of wiring to check, are there any common areas that go bad on a regular basis with these 4runners? All the battery connections look new and are tight. I haven't checked the fuse box though. I did how ever try changing relays and checked all my fuses. All of that checks out.

thook

No man, I don't mean the CEL coming on as a trouble code. Again, I only mean when you turn the key to ignition for ECU power verification. If it illuminates, as I explained above, everytime you turn the key, even when the no start situation occurs, that's a good thing. It's supppose to. It means there's not a problem somewhere between the battery and ECU, ie. relay, fuse, fusible link, etc.

Everywhere you see a connector, just check it. True, there are only so many critical components for starting, but it's not hard to check connectors and inspect what you can atleast see. This is basic troubleshooting. If you're not up for that, not sure what to tell you. Sorry to be a tad terse, but a motor's a complicated thing with EFI involved. Takes getting to know it a bit if you want to know how to fix it, eh.

As far as common areas, it's an old vehicle. It's common for things to break down, albeit slower for a well maintained vehicle. Especially a Toyota.... Anyway, things come loose, wires get brittle, things leak, blah, blah, blah. It doesn't help much that I can't see the vehicle. so I simply ask you look at if for me.

Here's some troubleshooting tips for you to peruse.....
http://personal.utulsa.edu/~nathan-b...63troubles.pdf

Good luck, ashtsi. It may be overwhelming and/or mysterious, but truly there's only so many things it could be. Eventually, you'll find it. Hopefully, sooner that later.

ashtsi

Hmm... Well i know when i did my best to disconnect the alarm the cel would come on when i turn the key, but as soon as i hooked it back up it doesn't come on. Either way it didn't start, but this makes me wonder why it doesn't come on when the alarm is plugged in.

Guess the only thing for me to do is start checking everything lol..

thook

If the alarm is connected and you're not getting the CEL, this means the alarm system is disabling power to the ECU. That's the only thing it could mean, provided your system is in normal condition. Again, though, I don't know anything about alarm systems, so I can't tell you how it would be wired in. Possibly the ignition switch, but that's a guess.