starting problem

[dmac]

I've run into a recent problem and i can't seem to figure it out. My 92 sc400 was running fine one night and the next morning, the engine would turn over but not start.

To troubleshoot i first changed out my fuel filter thanks from some advice from this forum. i've changed the ignition coils and spark plugs. i'm getting good spark from my wires. the spark plugs were less than a year old and they had quite a bit of carbon build up, which is a sign that it might have been running a lil rich.

next i bypassed the fuel ecu and there was no change. i next took off the iac valve and cleaned it. when i did this i left the valve off and attempted to start the car and she stayed idled just a few seconds longer than what was happening earlier. which is starting to tell me two things:
i'm getting spark, fuel and air to the engine.
i might be getting too much fuel causing flooding.

so now i'm checking why i would be getting excess fuel. fuel pressure regulator (fpr)?

so what i'm wondering is, if anyone has experienced this before? where the fpr is? and if there is more than one? or if there is anything that i'm missing :wtf:

 

[Lextreme II]

The fuel pressure regular is located near the throttle body. If you follow the fuel rail, it should be on your left hand side (facing the engine).

 

[dmac]

does that sound like the logical problem or is there something i might be overlooking?

 

[Lextreme II]

Try this. Put your foot on the gas pedal all the way down while turning your key to ignition. Your spark plugs build ups perhaps its too much fuel because your engine was not igniting. Try the above method and let us know.

 

[dmac]

i've attempted that and it cut off just as quick if not quicker.

 

[Lextech]

Just because you bypassed the fuel pump ECU doesn't mean you have fuel pressure. You need to check fuel pressure.

 

[dmac]

i've checked the fuel pressure its getting roughly 38psi. the issue isn't the lack of fuel its too much fuel. i also pulled the plugs that i just installed and found that the fpr side has significantly more carbon build up than the off side. which seems to me it could be an indication that the fpr is bad. if it was an electrical regulation issue both would be equally built up.

secondly is it possible for the air flow meter on the intake to go bad and indicate to the ecu that the throtle is wide open causing the steady flow of fuel and is there any way to test it?

 

[Lextech]

It is very difficult to help diagnose a car that is not in front of us to check out but, with that said is it possible you got some bad fuel on the last evening that the car ran? Also make sure you are getting spark from both coils-- if this is a V8 car, but they still will usually run on one coil.

 

[dmac]

i realize its difficult for you to figure it out without looking at it. but i'm looking at it and i can't figure it out either. i've switched ignition coils already as i mentioned in the original post. i've tested the spark and that's good too coming from the distributors. i'm just trying to figure out if the symptoms and what they're pointing to. i don't think any of the sensors, not including the air flow meter could be causing this problem. so what i've narrowed it down to is the ecu, fpr or afm. now out of these three there's only one that's under $1000. my question is whether i'm leaving something out or missing something or if there's another way to diagnose this problem to figure it out.

 

[Lextreme II]

Even the FPR have problem Like drop in few psi the car still start. AFM is possible, but the car still start (runs very bad). ECU possible. I have a 93 LS400 ECU u can try but i am not sure if it will work or not. I am sure a some with 92 ECU you can borrow. If you have fuel, ignition and air.... then you have some other hidden problem. Did u check all of your relays and fuses?

 

[dmac]

well i'm wondering if the fpr is stuck in the on position? if that was the case it would be flooding in the engine correct? which relays would i need to check/test in this case? and would i be able to bypass them with the traditional paper clip?

 

[stevechumo]

It could be the ECU. If you're not sure the fuel is dumping into the combustion chamber, then take the sparkplugs out and smell them. You'll know if there's gas or not after you try to start the engine. Check the throttle body and the TPS. If it's stuck, it would cause the problem as well. If you're sure the engine cranks healthily, then you don't have to do this. But if you're not sure, then try to unplug all sparkplug wires, fuel fuse and crank the engine. Make sure no wire touchs each other or the car's body. It should crank if the ignition parts/distributors are working correctly. However, you might have to switch to another healthy battery after you cranked too much.

 

[dmac]

the plugs definitely smell of fuel. and i've tested the spark coming off both distributors and that looks good. the engine cranks and as soon as it goes to idle it shuts off. when i cleaned the iacv it actually lengthed the amount of time the engine was firing. which seems to me as an excessive fuel problem.

with that in mind how does the signalling work between the afm, fuel ecu and ecu?

 

[Lextreme II]

I think i found your problem. I remember having the same problem a while ago. Double check you crank and cam sensors. I had an event that one of my cam sensors was dead and the car would not fire.

 

[dmac]

where are they located? and how do you test them?

 

[Lextreme II]

Here is a picture of the cam sensors below. Also u can test the Cam Sensors to see if they are still good. Secondly, you also want to trace the wires. Lot of time the fan belt might scratch it and damage the wire.

 

[dmac]

thanks for all of your help.
i've checked both of those sensors and they both ohmed out and looked good structurally. so i'm at a loss, the fpr is coming in today so i'm going to change out the fpr and see what happens.

 

[pops]

same problem

Let me know via pM what problem is as i have same exact ! Exact. My next thing is to replace throttle position sensor. I may wait to hear from you, if i find problem il let you know.
pops

 

[dmac]

alright now what?!?!?!?!?!

i've changed out the fpr and i'm good on holding an idle, no problems... however, now i can't put her in drive because she stalls out. any input? did i install the fpr wrong? what could be causing THIS problem?!

 

[stevechumo]

You need to diagnose the FPR with a pressure gauge and go with the specifications.