More of a RE-build Thread

[blindeyed]

[EDIT 10/23/17: I've gone through and fixed all the broken Photobucket image links, and instead have attached the images, so they shouldn't become broken again]

Like the title states, this is more of a repair thread than it is a build thread. Bought this truck for $1400.. over paid, big time. Here she is in all her glory

IMG_1428.jpg

And here she sits.. now

IMG_1470.jpg

I've been doing nothing but repair it. Previous owner said it ran fine without the MAF hooked up. Assumed it was just a bad MAF, and that's all that needed replacing. Nope.. I've got a can of worms on my hands. Been through 3 of those suckers, no difference in the way it runs. It runs rough and misfires badly. So this is my diagnosis thread of what I've had to do so far to figure this truck out.

Tally list so far:

• Swapped out the ECU with another one that functioned fine
• New O2 sensor
• Swapped out 2 more MAF's.. no change
• New distributor cap,wires, and plugs
• New fuel filter

There's probably more in there, nothing I can think off off the top of my head right now. I have checked all wires.. fuses.. any connections to see for corrosion. Can't find a thing. Vacuum hoses all looked great, until now since I hacked them up to remove the intake plenum and throttle body. I'm merely going on blind gut feelings now.

Which brings me to my current operation, replacing the fuel injectors with used ones that were on my old truck (which ran fine). I didn't bother testing the injectors to see whether or not they were bad.. I couldn't think of anything else that could be the problem at the time, so I started wrenching away. Got the intake plenum and throttle body off. Didn't realize until afterwards I didn't even need to remove the plenum to get to the fuel rail. Thanks go to the Haynes manual on that one!

IMG_1467.jpg

I've got the intake plenum reinstalled. Just waiting on the new O-rings to arrive to continue re-assembly. Apparently no auto parts store here carries on hand the rings that go onto the forward spraying end of the injectors. Think I'm gonna also replace the regulator as well while I've got it right in front of me.

But that's the idea of this thread. I'm going to keep updating it each time I replace or repair something related to this ongoing issue. Once I fix this truck, hopefully this thread might come in handy for someone else having a similar problem. My actual build thread will come once this truck gets running good.

[lush90]

I swapped a used japanese imported motor into my '91 and it idled fine but ran rough on acceleration, had the injectors cleaned and reinstalled w/ new o rings and it runs great. Are you sure the timing is set correctly? Has the timing belt been changed lately, which could have been an opportunity for the timing to be set incorrectly.

[blindeyed]

I'm no expert on timing, but from what I could tell it seemed to be lined up correctly. I had to replace the water pump right after I got it because it was leaking. Removed the timing belt to do so and while reassembling it I made sure to not move the crank or the cam. Before I removed it, I set it to TDC. Can't say for sure if the camshaft was lined up perfectly. The timing mark wasn't exactly easy to find. It was really just an educated guess with the help of a crappy Haynes manual.

And since I'm a little terrified of messing with timing, I'm saving the distributor and any timing adjustments for last. I'm worried I'll just mess things up even worse. One of those situations where I would feel more comfortable with an expert looking over my shoulder and teaching me ya know. I've watched dozens of videos and read countless articles on how to set timing.. but nothing was really clearly explained enough for me to grasp.

Weird thing is, when the mass air flow isn't plugged in, the computer goes into "limp" mode and mechanically it will run fine. No misfires, or bogging down at all. But doing so, it will get around 8mpg, and the exhaust manifold starts glowing red hot. After I realized that I parked it. So it's been hard to tell if it's something electronic somewhere (despite all the sensors I've swapped out) or if it's something mechanical related.

[4doorciv]

Don't loose hope man. I replaced my injector o rings with some grommets at home depot. Way cheaper then the dealership, but this in on a dsm 4g63 in my max. Hope you find the problem soon. Oh, and try to test for fuel pressure and vacuume. A vac leak can lower idle and a big vac leak can cause a really bad stumble to a stall. Similar to the mpi relay acting up causing bad fuel pressure.

[blindeyed]

Similar to the mpi relay acting up causing bad fuel pressure.

What is this MPI relay you speak of, and where is it located? Haven't heard of it.

Definitely not giving up hope, already did that on my last truck and sold it. This time around, if I gotta replace every bolt on this truck to get it going then so be it.

[4doorciv]

The mpi relay is the fuel pump relay I believe. I have on on my eclipse wiring harness that is closest to the ecu. I seen one on lsr mike's truck in his picture thread of his buildup. I am not too sure if yours is in the same place though.

[blindeyed]

Oh ok, that's the relay which I heard was the combination starter/fuel pump relay. It's cranks right up, so I'm assuming it's okay. But knowing my luck with this truck, who knows lol

[l.k.]

sorry about your tough luck..i would check the timing from every angle man. that is a must. But like 4doorciv said about the infectors. I have had many vehicles that did that and it was the injectors...dirty, clogged, etc.

when its in limp mode..it is just dumping fuel to compensate...thats why bad gas mileage and red hot manifold...its firing so hot, in one cylinder, then the bad injector is getting enough gas since its dumping so harshly. The others that are fine are overloading ...but they are burning some and some is getting sent to cylinders. It can cause vapor lock. all kinds of others problems....'
one time with my blazer it vapor locked and then once burnt a hole in piston....from being too hot when firing with too much gas in limp mode....

good luck

[4doorciv]

On my eclipse moi relay, it doesn't send a signal to the starter. It actually reciebes a signal from the ignition or starter to actualtr the fuel pump for startup, then the ecu takes over and sends voltage or grounds something to keep it going. There is also a test connector to check fir voltage or can be used to jump the fuel pump to turn it on manually. I am not too sure how similar your wiring harness is but I would check for voltages at the relay and see if they are in specs. Not saying the relay is bad or anything but that relay is important to start and keep the truck running.

[l.k.]

On my eclipse moi relay, it doesn't send a signal to the starter. It actually reciebes a signal from the ignition or starter to actualtr the fuel pump for startup, then the ecu takes over and sends voltage or grounds something to keep it going. There is also a test connector to check fir voltage or can be used to jump the fuel pump to turn it on manually. I am not too sure how similar your wiring harness is but I would check for voltages at the relay and see if they are in specs. Not saying the relay is bad or anything but that relay is important to start and keep the truck running.

funny that you brought that up...my friends eclipse did the same thing...friend told him to check this, replace that and bam.

[4doorciv]

I researched and researched, and had it all drawn out. I needed certain wires energized by that relay and needed it wired up a certain way to make my dsm truck start and run. It was burned in my head while I was doing the swap, but it's only bits an pieces I remember now.

[blindeyed]

Finished putting the truck back together, only to receive more disappointment. All new o-rings on the injectors.. All injectors, and fuel rail w/FPR were swapped over from my old truck that ran fine. To make it easier to explain what the problem is, I just went ahead and made a video with my crappy camera. So here, ya go:

[*Sorry, deleted the video*]

It's getting fuel, it can run.. but doesn't. All I can think of is something electrical somewhere is messed up. Sensor, relay.. something. I am so stumped, I have no idea what to do next.

[4doorciv]

So what did you find out caused the no start problem? I'm glad to hear it started. Well the mpi relay stays energized by the ecu. If not then check your ground connections around the ecu, there should be one at least. If not more. Also make sure the maf is plugged in because that is what senses engine load. The coolant temp sensor also tells the engine how much fuel to dump. Incorrect readinds can cause a start then stall problem, engine flood with gas, or not enough gas. Aren't you glad your that much closer?

[blindeyed]

Never had a no start problem, it would always start, but die off. Couldn't ever keep the thing running. In the video it would almost immediately die right after you start it. I found out I forgot to hook back up a vacuum hose that goes from the valve cover to the intake manifold. Now it runs about 3 times as long before dieing off. I'm almost certain now I have a mysterious vacuum leak that's eluding me. I could be wrong, but it's about the best lead I've got to go off of now.

Thanks for the tips, I'll def keep those in mind and take a close look at them

[camoit]

Just something I see in the video. I saw that when the MAS was plugged in and you would start it the hole thing would move like it was plugging the air box. Then with it unplugged it would not move nearly as much. Look at the video. Oh Oh. I see it.... It's a bad radiator cap...

[l.k.]

........

[crvtec90]

What year/make/ model did you get that mass air flow from? Im not sure it is what you need for your motor. :D

[4doorciv]

Intetesting. So you suspect vacuum leak causing your stall? Is one of the sensors the coolant temp sensor? That one sensor can really mess you up and cause the ecu to dump fuel. Maybe look at both.

[blindeyed]

........

Mass air flow plugged in, motor stalls out after a couple seconds of running. Mass air flow unplugged, motor runs fine in limp mode.. that's about the jist of it.

What year/make/ model did you get that mass air flow from? Im not sure it is what you need for your motor. :D

Ditched the one I picked up in the junkyard. Used the CRC MAF cleaner on the sensor that came on this truck, and the old one off the other truck. Same thing happens.

Intetesting. So you suspect vacuum leak causing your stall? Is one of the sensors the coolant temp sensor? That one sensor can really mess you up and cause the ecu to dump fuel. Maybe look at both.

I suspect it now because I got a few more seconds of run time after hooking the vacuum hose back up that I left off. Kind of hoping maybe there's another mysterious vacuum leak somewhere.. it's my best guess at this point. I haven't touched the coolant temp sensor, because there's about 3 different sensors right by the thermostat housing. It's a little confusing as far as which one is which. I imagine one is for the gauges, one is for the ecu.. and the third?? fan possibly? No idea, haven't researched it any. Any info on that is greatly appreciated.

[dmr8x2]

sounds like you may need to find someone with an Comp to talk to the ECU
and get your codes.

[crvtec90]

Coolant temp sensor for computer is the one screwed into the top of the thermostat housing sticking straight up in the air with 2 terminals on it. Probably a yelow wire with a green stripe .... and a black wire.

[4doorciv]

If I remember right, the sensor plug looks like a T. The one for the gauges is a single wire, and the fan switch is the third.

[blindeyed]

Great news! The truck is running!

To all of those who posted, thanks a ton for your help! I did some more research last night on the coolant temperature sensor, and 4door, you nailed it on the head. Computer relies on that to help determine how much fuel to dump. Took the old one out, it was nasty, gunked up and corroded. New one in, it no longer stalls out after a few seconds of running. However, it was still running horribly as if it were about to stall out.

For shits and giggles, I figured I'd play with the distributor and try advancing/retarding the timing to see if that helps. What do you know.. it purrs now. Well, not really, the exhaust manifold leaks badly at the down pipe connection so it sounds like crap.. but compared to before, sounds like a freakin BMW.

Goes to show how simple the solution really can be. Not to mention how dumb it can make you feel for not thinking of it earlier

Haven't taken it for a test drive yet, probably will in the next couple of days. Will report back with more then.

[camoit]

So it's like flying in a Cessna airplane.

[l.k.]

Lmfao^^^^^

glad to see you got it running better man......