Returd

92 SC400 no start

I just tried to fire up my 1UZ. Pretty sure I have a no spark situation. Car ran fine prior to some pretty significant work.

I did valve clearances and as such had the valve covers, spark plug/coil wires out.

I also ran new fuel lines.

I charged the fuel system with a couple of rotations of the ignition key until I didn't hear the pump run.

Engine turned over easily but not even the hint of firing up. I sniffed the tail pipes and smelled gas. I also removed the air filter and gave a shot of ether, no hint of starting.

I did a once over under the hood looking for something I missed, but everything seems in order.

I believe I've reconnected everything but obviously missed something.

Anyone got a suggestion of where to start looking for something I failed to connect properly that will result in no spark, any cylinder?

I did not mess with the ECU btw. I have a freshly rebuilt one to go in but it's unproven so I wanted to test start and drive the car to make sure all the other work I've done is working properly.

I did replace the steering rack but don't recall getting close to anything under there that could cause an issue.

The work was all done over the winter so I don't have exact recollection of everything.



plugs, wires, rotors, caps are very recent, done about 2 weeks prior to my doing the valve clearances.



Are there any fuseable links in the ignition system? I did a bit of chassis welding and am wondering if I may have blown a link. Alternatively are there any fuses or relays that could be blown?

oldManTan

since you worked on the steering rack make sure you didn't damage the wiring on the crank sensor or the sensor itself. car won't start at all with that sensor not working.

if you're not getting fuel pressure the spark plugs won't fire either. first make sure the vacuum lines are routed correctly to the fuel pressure regulators. without good vacuum they won't work.

in the diagnostics port on top of the engine jump pins B+ and FP to put the fuel pump in 12v mode, that will confirm that you should have good fuel pressure and you'll audibly hear the fuel pump, it's pretty loud.

check the connections on the ignition coils obviously but you've probably done that

make sure your cam sensors are connected they're underneath the cam gears

that's all i can think of for now, hopefully it helps you some.

Returd

I’ve checked few of the things you’ve mentioned, changed the crank sensor. I think it’s tie for me to get super methodical and measure resistances etc.

I have got it running but now it’s hunting for idle and bogging with misses nd backfires in the cats or internal to the exhaust when I give it gas.

Your fuel pump and vacuum suggestions give me some hope that is’s something simple like that.

I swapped the ECU last night with no change.
I’ve been wondering if maybe thee’s a harness problem since I had to move the injector/ignition harness to get valance covers off for my valve clearance job.

One step at a time though.

oldManTan

if you did valve covers you probably took the throttle body off too right? make sure you didn't move the TPS by accident, hunting for idle is usually the TPS. i think the best way to adjust the TPS is to start with it turned as far left as possible where your idle will be really low and if you give it gas it will jump around with the RPMs. then turn the car off, turn the TPS a little to the right, tighten it back down and try again until your full RPM range the car revs fine. i'm having the same issue, just got it to idle normally with a small misfire here and there that i'm not worrying about anymore.

i'm gonna run some seafoam through mine, hopefully that fixes the idle. you can also try cleaning the IACV, make sure you lube up the worm gear otherwise it just binds up and doesn't move.

Returd

Prior to tackling this job I had my intake off and cleaned all the coked fuel out of the upper, lower and throttle body. I also Sea Foamed mine. Car ran fine afterwards.

I did have the throttle body off for this most recent job (as well as the last one). I have not tested or adjusted the TPS yet. I will and found a useful video on that from CartuneNZ on YouTube. From the patina on the throttle body I can see the TPS didn't move but will test and adjust just to rule it out.

I have not jumped the fuel pump yet but it's on the list. I checked the vacuum lines and everything is in place correctly, but that doesn't rule out a vacuum leak. I may string new hose if I can fine a reasonably priced reel of hose. Vacuum line to fuel regulator is correct. I have not lubed the IACV.

I checked timing tonight and it looks good. zero degrees at low idle (hunting a bit) which is under 1000 rpm.

Driver side coil tested fine primary and secondary.

I'll test the passenger side tomorrow as well as re run the spark plug wires in exact routing as specified in the manual. They took the time to lay it out so I'll take the time to follow it.

Returd

tonight I metered the cam sensors; good
plug wires; good. I rerouted the plug wires exactly as shown in the manual.
I metered the passenger side coil; good (did driver side last night, good).

still running like crap.

I popped open the diagnostic port and the contacts were packed with lithium grease. I'm sure it was an anti corrosion measure. I cleaned it out with contact cleaner and an air line.
Gonna try the fuel pump jump tomorrow.

I also added 5 gallons of gas and noticed a big inhale when I popped the gas cap.

I left the cap off when I test ran the motor, no difference.

I'm working my way through all the checks in the manual

Returd

I’m going to recheck the timing, trying to hold rpms at the 700 rpm recommended by the manual. If the timing is out I’ll assume I jumped a tooth on the belt.

Does anyone have an easy method to move back a tooth?

Do I need to remove the tensioner?

My mechanic buddy said that you should never turn the motor over backward (by hand obviously). This comment applies to timing belt engines, not timing chain engines.

I did this on several occasions when shimming valve clearances. This has me thinking I need a better check on timing as I may have indeed jumped a tooth.

Returd

well I'll say I live up to my "Returd" handle

I did a second check and have discovered my valve timing is off. It might be a day or two until I have it corrected. I'll report on results

Duh

I'll repeat what my mechanic buddy said. With timing belt engines, don't turn the engine in reverse. I did that several times when setting my valve shims.

Good thing it's a non interference engine.

Returd

so I removed the timing belt tensioner but the belt tension is still pretty good. I have the drivers side distributor cap off and I was hoping to get enough belt slack to turn it to proper position. Doesn't look like I'll get enough slack. Any hint on how to clock the camshafts independently with the belt still in place?

oldManTan

i have no idea man, but i think one of my cams might be a tooth off too because i have code 13 with no issues regarding the cam sensors. curious to see if you figure out a way to get enough slack on the belt without full engine disassembly lol.

Returd

I pulled the front distributor covers, removed the distributor housings and got slack by rotating the passenger (right) cam pulley counter clockwise. I have the belt off from the passenger pulley.

The belt has to come off the passenger pulley, there is a lip on the driver side pulley that prevent belt removal.

I’m trying to get things clocked now.

oldManTan

awesome, you should make a video to show how to adjust timing if it's off, that would be really helpful especially for this engine.

Returd

I got the timing correct after several tries.

I still have hesitation at initial throttle input but it revs out. I let the engine warm up and the cats got super hot. I'm thinking it was running rich but will investigate through the week.

The manual states to use paint marks on the outgoing belt. Each cam pulley has a TDC mark as well as the crank and the manual suggests a mark on the belt at the lip of the hydraulic fan oil pump. With the cams and crank being out of time it took me a few tries to get things clocked. I went one tooth to far in either direction on both cam pullies. I also had a couple of screw ups where the belt moved on one pulley and I didn't notice. I also inspected the cam sensors and replaced one as the ground wire was one sneeze away from detaching.

You don't need to pull the rad. or disconnect the hydraulic fan.

You do need to pull the radiator reservoir.
pull the top rad hose
disconnect the bottom rad hose and wedge it out of the way.
remove serpentine belt
alternator needs to be unbolted but can be rested on the power steering lines so the plug and wire can remain connected.
front left and right plastic belt covers must be removed.
distributor caps, rotors and housings all need removal.
idler pulley need to be removed.
Belt tensioner needs to be removed and compressed.

The manual says to pull spark plugs (to release compression). I did not but be aware that the cam pulley will snap out of position if you don't keep a socket and bar on the nut holding the pulley to the camshaft.

Now you're ready to adjust.

I positioned and set the left (driver) cam pulley first and used a couple of spring clamps to hold the belt onto the pulley.

I then set the right (passenger) pulley


Paint marks and patience are key.

I got pretty good at it with all my overshoots (mistakes). I got it down to about an hour, but the first time took about double that.

oldManTan

awesome to hear, initial throttle hesitation is usually a TPS issue, at least that's what it was for me, adjusted TPS and throttle is fully responsive at every point.

Returd

tonight I set TPS gap as per this video


I didn't test the TPS itself but will do so tomorrow. The gap was greater than .010"

I gave it a quick test start to little difference. I decided earlier today to clean the IACV so I removed it and cleaned it out, then re-installed. Another test start and it ran more poorly.

On a whim I decided to test the right coil for spark, and got a very weak spark against the valve cover and then engine hook.

The interesting thing is that the engine ran pretty well on 4 cylinders, with the typical hesitation I've been having. I swapped out (but did not test) another igniter, no change. I then reversed the igniters, no change.

I tested the coil wire, very low resistance 3-4 ohms if I remember. I then pulled the coil and tested. It was almost out of spec, so I tested another one from my collection of harvested spares. The replacement was middle of the spec for primary and secondary resistance checks.

So I've got a weak spark condition from a seemingly good coil.

More head scratching to do.