KazumaUCF20

Hello everyone, before I start this I have read majority of threads and most aren't to solve my issue. Im currently dealing with a crank but no start issue on my 1994 Toyota Celsior UCF20 non vvti(I see the two are practically identical so im here). Heres some backstory. So at first this car started and ran like butter, 1st turn and on. Only issue for running is that the car would surge due to a bad IACV(to my knowledge) and the temp sensor was replaced to tackle that more. Once I started to drive it more it would be fine cruising or wide open throttle. Then one day it decided to stall and not turn over anymore. That same night I sprayed starting fluid in it and eventually I got it to run on its own. So boom fuel issue right? And proved I have spark. Lets venture on further. So I seen one of the most common issues for intermittent starting and stalling and such is due to leaking capacitors in the ECU. So I went ahead and replaced all of them. Still nothing. I have fuel at the rails, the fuel pump indeed does work and can clearly hear it when trying to crank the motor. I feel like my injectors are not firing or at least getting pulse. When I initially try to start the car you can hear it fire slightly then nothing and continues to crank. Whats weird to me is when the car would stall I loosened and retightened my intake pipe connected to the throttle body. Then it would start , well thats not the case anymore. While the car ran I did do the brake clean trick to check for vac leaks, nothing. Im so damn stumped on what it could be. I know theres 4 ground wires from the ECU that lead to the injectors and one orange/black wire for 12v but im almost certain theres no open circuit between them considering how it ran before. Is there anything anyone can give me a lead on for injector firing? I have wire diagrams and all to trace anything. I just dont know what else would cause this issue. I ruled out fuel pump/filter/FPR, I replaced the crankshaft position sensor, I checked the EFI Relay/Circuit Open Relay/Fuel Pump Relay and they are all properly functional . Im stuck and just want to drive this car. If anymore information is needed I will provide it.

timmy0tool

iTrader: (7)

does the car run with starter fluid now? yes you hear the fuel pump but is the flow enough?

one way to check is this:

KazumaUCF20

Not anymore no, the battery is getting low from all the cranking so Imma charge it and let it chill for a bit. I tried jumping the +b and fp and still wont run. Idk what to do. Its becoming more and more tedious. I have reason to believe its in an inhibitor mode? But if bypassing the fuel pump stops that then this seems like injectors are the problem. I might just try and find a known good ECU to use and see if it runs off that. If it doesnt then I know something is going on with either a sensor or wire.

joshuaho96

Pull the fuel pump fuse so you aren't potentially flooding the cylinders. Then put a timing light on cylinder one. Make sure it's actually sparking at a sane base timing. Make sure the distributor is actually timed correctly and it's not 360 degrees out. Check all 8 cylinders with a timing light and make sure the brightness is consistent and the spark is happening at a regular interval. If you have spark leak it'll manifest as multiple weak lights or no timing flashes at all. Once you've confirmed you have spark verify you have fuel pressure at the rail when you flip the key on. If you've verified the fuel rail is getting good fuel pressure (3-3.5 bar) while cranking then it's not the fuel pump or pump control. If the fuel pump isn't turning on make sure the immobilizer system is functioning and allowing the fuel pump to run. After cranking with the fuel pump fuse plugged in pull the plugs and verify there's fuel on them. If it's dry and doesn't smell like gasoline at all put an oscilloscope on the fuel injector plug and verify the ECU is sending pulse width. If it isn't verify that your ECU is actually sending the injector pulse at the ECU plug before you conclude it's an ECU fault. This is a lot easier to do if you're willing to build this TDCL cable and software which will tell you the ECU's commanded injector pulse width: http://toyota.kgbconsulting.ca/wiki/...ace#Data_cable

If you don't want to do oscilloscope or arcane old computer nonsense try a compression test first to make sure it's not just a broken engine. Also pressure test (lightly, like 3 psig through the intake) the engine to see if you can find air leaks. Also try cranking with the MAF unplugged. If it runs without the MAF briefly I would suspect the MAF sensor has issues. Save the complicated annoying tests for when you've eliminated everything else.

KazumaUCF20

Im fairly certain its ECU through all the testing, even after repair it must be other components inside going bad or gone bad. Ill update the thread on what else I’ve done when I do it.

KazumaUCF20

Alright this is a delayed update but I’ve gathered everything I could. Both cam sensors have been replaced, crank sensor has been replaced, maf has been replaced(I have oem and 2 other good oem ones), FPR has been replaced, fuel filter has been replaced, ECU has been replaced with a known good one(no immo), relays have been swapped just in case, I know I have spark(will run off starting fluid but dies without spraying) I know I get fuel to the rails, I have dampener indication and tested fuel pump. I have VISUALLY seen injectors fire, there are no vac leaks. Im genuinely stuck and lost. I could replace spark plugs but im sure the motor would at least run like crap if they were that bad. I honestly dont know where else to go. This motor did not jump timing , the engine has barely 86k miles on it, I dont have rusty fuel lines as this car is rust free. I’ve bypassed the resistor through bridging the b+/fp. For the laughs yes, its in park. If anyone has any leads or in depth detail on what it could be please let me know. The current status is the engine will fire for a brief period, actively hearing it fire then loses fuel during the cranking process. Igniters are functioning properly as well if that came to mind. Any help is appreciated, sorry for being a pest to anyone haha.

joshuaho96

You have replaced a lot of things but what have you measured? What is your fuel pressure? Does the engine have good compression in all cylinders? Is the fuel in the tank good? Is injector pulse width normal? Have you had the injectors tested off of the car for proper function?

The act of measuring these things will often raise more questions than answers, but chasing those questions will get you to the ultimate answer instead of just guessing blindly.

KazumaUCF20

Pressure was a healthy average of 3 bar, compression without having to even really test it I know for a fact is good, I know the “you never know” and its rules out a variable but on a realistic pov, this motor has barely 86k miles, was babied, and drove with not a single hint of bad compression or anything for that matter. No misfires or weird acceleration. As for injector pulse I have not measured it but Im simply gonna rule out that variable with the ECU being repaired properly. There is no chewed or frayed cables, its honestly a mint car aside this headache. As for bench testing the injectors , as much time and money it would cost, im perfectly fine with replacing them with a whole new set that yes would be bench tested before purchase. The fuel in the car is fresh , a whole tank of it, along with a filter being replaced. From other experiences in other cars when I try to start it will subtly fire then quit, which to me sounds like a fuel cut off. This cut off isnt fuel pump either , its injector only as I’ve stated previously I jumped the fuel pump and kept it running on key. So ultimately as everyone has told me even though I swapped it, this seems to be a ECU issue. The other ECU I have is a USDM one yes , but will run a JDM motor. Unless Im being lied to in all ends of research and expertise in them. So I’ll have my original one refurbished and completely rule that out. Its just annoying seeing other UCF’s clapped beyond belief , parts barely hanging on, rusted out, and abused . Yet mine throws hissy fit in its fairly mint condition. Little cry baby rant haha. I’ll continue my DD, and hopefully provide insight for others in the future to solve any issues that are similar to mine.

Yamae

I noticed that the way you troubleshoot were mostly to replace parts next to next without measuring/confirming waveforms and the phases. I'd simply start to check the timing of G and NE as is shown below. Computer controlled cars need an oscilloscope for the troubleshooting. Without it, you'd waste your precious time and money. ie: You can find what are G1,G2 and NE at here.

KazumaUCF20

For the most I do just replace and call it a day, but this unit is gonna have me go in depth as its simply showing just replacing isnt working. Im familiar on measuring and testing , but as a unit thats in a backyard rn, my tools are limited. I will obtain an oscilloscope and do what Ive done to the headaches of BMW’s. I appreciate the diagram as well. I’ll put that caveman ideas aside , because I’ve mainly just been wanting to get this out the way and brush past the in depth diag. I get it, trust me I know its most necessary path. Just wish it was more simple for me this time.

KazumaUCF20

Finally found the issue after a truck load amount of testing/diag , and eventually found inconsistent voltage to my driver(passenger for US) coil. The two pins on the female connector fell loose out of the connector itself and was barely making contact to the coil. Luckily I had a spare connector to replace it, soldered and she runs beautifully again. To add, a USDM ECU does work for JDM models btw, you’ll just have a CEL because theres no emissions monitoring on the japanese models. This is for a UCF20 Celsior from 94 and grabbed an ECU from a 95 LS400(first year for UCF20 in the US I believe). The original ECU still worked as well but has some damage to the board itself but was able to confirm successful repair to the capacitors. It will be sent out and professionally repaired so it can be put back in. I know I was a replace vs diagnose guy in the first half but thats usually how it goes with my luck in minimal diag figuring out what the problem is. This car made me use everything for something so simple yet “hidden”. Thank you everyone for all the help provided , and will most definitely be using the material given on future problems for others as well.

hereforthedough

glad to hear that you've resolved it!