Grabbit89

So I've dug through the forums to try and figure out my cold start problem to no avail. A little history on my truck. I got a automatic trans 94 SR5 with the 3VZE from my brother in-law as a non-runner. He was having problems with it and dug into it with no real direction so there were pieces pulled off at random. Symptoms were poor mileage, low power and rough running and starting issues. I was new to Toyotas and unwisely threw a bunch of parts at it thinking that would correct the issue. Big mistake... Right now it cranks over but refuses to fire. Maybe one or two cylinders fire after the first few revs but nothing after that. I know its getting fuel, I can smell it in the intake, tail pipe and when I've swapped plugs the ones coming out are wet. I did get it running a week ago but it was reeeally hard to start initially. I set the timing once it was warm and adjusted the idle speed to factory. Restarts when warm were not a problem. Since then I have not been able to get it started. I've read that low compression can create this scenario. I did drive the truck once around the block when I got it running a week ago and it seemed fine on power and sounded like all cylinders were firing. Since then I've parked it outside and it will not start.

Anyway, a quick list of what I've checked and/or replaced:

System Checks:
-Zero fault codes (constant blinking light with terminals jumped)
-Fuel Pressure is dead on at factory PSI spec (cant remember the value but it was as spec'd)
-Injectors getting fuel (replaced almost all of the fuel system components, I can also hear them when the MAF flapper is manually moved)
-Verified cold start injector is working (with key on) and also not leaking
-Verified distributor is timed correctly (pulled it out and verified)
-Ohm'd out multiple coils I've tested with
-Ohm'd out the Ignitor and distributor
-Checked spark on all wires grounded at the throttle body. Spark seems week but its there.
-Replaced and checked all vaccum lines
-Cleaned out a ton of carbon from intake mani

Parts replaced or tested:
-Timing Belt and associated tensioners - replaced
-Knock sensor - replaced (big $$ factory part)
-Injectors - had the factory units tested and rebuilt by Dr. Injector
-Fuel Damper - replaced
-FPR - replaced
-Fuel Filter - replaced
-Cap/Rotor/Plugs (multiple sets of all)
-Coil - tried three different ones, two new and the original
-Battery - new heavy duty one, 750CCA I think
-Coolant temp sensor - replaced

Any ideas?

scope103

So ... are you waiting for one of us to say "check it"? Given what you've spent on parts already, I think you can spring $20 for the tool.
Make sure the plugs are firing in the right "place." Remove the upper timing cover so you can see that the two cam sprockets point "up" when at TDC. Then pull the distributor cap to confirm the distributor is pointing "near" #1. (You can have the distributor out 180° and it will look like the timing is right. Probably not your case, but now you've got to be systematic.)

Use your timing light on each plug lead; if the light flashes, the plug is firing (me, I don't think "weak spark" is a thing; if it fires, it will ignite).

Unplug the CSI and try to start it. If the CSI timer switch is stuck closed, you could be flooding.

Try to start with starting fluid. If it will start then, that points to a fuel problem.

Are you sure the timing was set with the jumper in place (to force the engine to "base" timing)?

(kudos for admitting that throwing parts was a doomed attempt ...)

Grabbit89

^ Thanks. I ordered a compression tester and plan to test this weekend. I'm a bit hesitant to reply comp indications from a cold engine though.

-I have checked the distributor timing, the bigger tooth is aligned with the two notches on the stalk. I also verified the engine was at TDC when I put it back in. One thing I didn't do was jumper the diagnostic port for base timing when I set it. My bad, guess I'm not used to having to do that.
-As for the cold start injector. I've tried both with it unplugged and plugged in. Same result.
-The reason I say it seems to have week spark is that compared to other cars I've troubleshooted before, the visible spark seemed weak and inconsistent. This could have been how it was grounded but not really sure. What symptoms does a bad igniter introduce?

scope103

Here's the FSM for the igniter "test." Note that Toyota doesn't ask you to assess how "strong" the spark is; just that it is present. http://web.archive.org/web/201212070...12onvehicl.pdf

Here's the FSM for setting ignition timing. (The "SST" is a paperclip.)
http://web.archive.org/web/201501160...e/64tuneup.pdf
You don't (really) set timing, the ECU does. But your truck doesn't have a camshaft position sensor, it uses the coils in the distributor. But they have to be set to "point" to the right place to start from. The jumper tells the ECU "don't try to advance/retard timing due to temperature or anything else; just leave it at base timing."

The manual advises that the timing should advance about 2° when you remove the jumper. In my experience, that doesn't always happen. I think it is possible, under certain temperature conditions, that "regular" timing just happens to be the same as base timing.

Remember that there are TWO TDCs for each turn of the distributor. If you install the distributor when the crank is at the top of the Exhaust Stroke, rather than Compression Stroke, your timing light will look good but you'll be off by 180°. The only way to check this is to verify that the cams say "top of compression stroke on #1" when at TDC. Since you have to pull the upper timing cover to tell, do the compression test and timing setting first.

Grabbit89

Right, I should've clarified. I set the distributor timing when the upper timing cover was off because I wanted to make sure the engine started before I put all the belts, hoses, fan back on and filled the radiator. They were dead-on on both cams when I did this.

Grabbit89

So I attempted a normal compression test this weekend but ran into issues. It was a warm day (temps in the mid-70s) for the PNW and the truck started, albeit roughly, when it was cold. I ran it for 30 minutes or so and drove it around the block. I had some white smoke once it first started and then blue once it warmed up. I pulled it into the garage for the compression test but got side tracked. I attempted the same the next day when it was colder but couldn't get it started in the garage. I figured I'd try the compression test cold and the results are all over the board. Check it out:

#1 = 92 psi
#2 = 45 psi
#3 = 71 psi
#4 = 52 psi
#5 = 70 psi
#6 = 140 psi

I'm leaning towards weak compression being the cause. Warm starts are no issue. Probably the engine needs rebuilding in that case...