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Alright all, this car is starting to give me a headache. So first off I rebuild the whole fuel system in the car from fuel tank back to rebuilding injectors. I've taken that rats nest apart multiple times. I initially changed cleaned fuel tank and replaced fuel pump with a quantum fuel pump. Car started when I did that and held good. went back the next day and car didn't start. Looked back at the video I made of the car resurrecting itself and saw what appeared to be fuel shooting out from top of engine in mist form. I suspected maybe my fuel injector seals may have broke from sitting so long. Sure enough the cap broke off and all the seals were basically apart. Cleaned injectors and replaced seals. After putting engine back together, I started engine and it started. This time it ran and it died out on its own after about a minute of holding. It was late when I started it so I figure I start again the next day. Started next day and nothing. Checked for sparks and all plugs were shooting sparks and I already replaced these so I know plugs are good. Checked Fuel system again and found fuel pump wasn't pumping fuel. Checked fuel relay-good voltage. Checked fuel pump wire harness-good voltage. Checked for check engine codes and found throttle sensor (full range) and throttle sensor (narrow range). Checked throttle position sensor and all readings read good except for full open on bottom terminal. It was reading about 2.8 when it should be closer to 5V. Tried to adjust but couldn't get in range to 5V. Most I got was 4.8 but all the other numbers were way off. I'm out of ideas and I feel like its something relating to ECU communicating something not being in specs so not engaging fuel pump. I could really use the help. Thanks
For an engine to start, you need Compression, Air/Fuel, and Spark (at the right time). Assume you are dealing with a fuel issue, or at least count that out as not being an issue.
I would check the plugs to see if fuel is getting in the housing. Are they wet with gas. If not, you probably have a fuel issue. If they are, it's a compression or spark issue.
If it's a fuel issue, do you have good fuel pressure. If you do, it's probably an injector issue. If not, it's probably a fuel pump issue. These issues could be wiring related or control related, you just need to isolate the unknowns. You can start by checking the voltage at the pump. Also, if you have the stock ECU, you can check fault codes. If not, you could swap back in the factory ECU (if you have one and if your car is not heavily modified) to check if there any codes
Turn the key to run and manually open the AFM door. Can you hear the fuel system?
sorry I misread that. I have an FD, no AFM on it. But like I said, i disconnected the line from firewall as well as straight from fuel pump housing and check both points by itself and no fuel is coming out of them. I checked voltage to make sure the fuel pump is getting voltage and it has voltage. Checked all my fuses and relays and all good. I think something rom sensor related is prevented it from turning on my fuel pump.
For an engine to start, you need Compression, Air/Fuel, and Spark (at the right time). Assume you are dealing with a fuel issue, or at least count that out as not being an issue.
I would check the plugs to see if fuel is getting in the housing. Are they wet with gas. If not, you probably have a fuel issue. If they are, it's a compression or spark issue.
If it's a fuel issue, do you have good fuel pressure. If you do, it's probably an injector issue. If not, it's probably a fuel pump issue. These issues could be wiring related or control related, you just need to isolate the unknowns. You can start by checking the voltage at the pump. Also, if you have the stock ECU, you can check fault codes. If not, you could swap back in the factory ECU (if you have one and if your car is not heavily modified) to check if there any codes
Good luck
thanks for all these suggestions, I checked majority of these. I have a stock ECU and was able to pull up 18-throttle sensor narrow and 12-throttle sensor wide. Tried to adjust but a little hard to get true numbers without warming up the engine. But I did narrow it down to being a fuel problem. Just can’t figure out why my fuel pump isn’t turning on. Has to be a sensor or safety issue
Have you narrowed it down to the fuel pump not operating? If you have, you need to determine if it's the fuel pump itself, or the control system. If you are getting voltage at the pump, then it's probably a bad pump. If you are not getting voltage, it's a control system issue. Check page F-30 in the '93 Service Highlights, This give you a simplified version of pg Z-28 in the '94 Wiring Diagram. You will need to trace back and check each component in the the fuel control system to see where problem is.
Things to check is the FP connection at the bulkhead. This sometimes gets fried if you have an aftermarket FP (to include the Supra pump). Also check the ignition switch. This limits voltage and there's a mod to bypass. Next would be the relays. The resister usually goes bad. And by checking, check both the components and the wiring (resistance or voltage at the componant)
Have you narrowed it down to the fuel pump not operating? If you have, you need to determine if it's the fuel pump itself, or the control system. If you are getting voltage at the pump, then it's probably a bad pump. If you are not getting voltage, it's a control system issue. Check page F-30 in the '93 Service Highlights, This give you a simplified version of pg Z-28 in the '94 Wiring Diagram. You will need to trace back and check each component in the the fuel control system to see where problem is.
Things to check is the FP connection at the bulkhead. This sometimes gets fried if you have an aftermarket FP (to include the Supra pump). Also check the ignition switch. This limits voltage and there's a mod to bypass. Next would be the relays. The resister usually goes bad. And by checking, check both the components and the wiring (resistance or voltage at the componant)
Good luck
First off I went back and checked my connections especially on the fuel side and seen the fuel from my secondary injectors had a small kinked line in it. I had to change that line out since it ripped off on removal. I guess the angle is too sharp so I put a hose clamp on the kink and tighten it till it made a solid circle shape. Nothing else looked wrong. Started and again nothing. Pulled the main fuel line off from fire wall and this time fuel came out of line. Tried to crank with line out and very low pressure from that line. Hit a dead end so decided to educate myself with this info and this is very helpful. There's tons of information I was searching for. Only thing is I cant seem to find the Specs of what the resistor is supposed to be pushing out if its a good resistor. I figure I start from there and possible have to work my way back to the ECU at some point but cant find the specs for that as well. I seen the ECU controls the fuel pressure for start ups and may point me in the right direction for which sensor could possibly be bad if that is the situation. But I'd like to start with the resistor first since I did install a stronger fuel pump. Any advice where I can find specs for it?
Forgot to mentioned that I changed out my upgraded fuel pump to a new stock one. Tested the aftermarket one and hooked up directly to battery and still a strong fuel pump. I'd have to say I'm pretty confident it isn't the fuel pump that's the issue.
You may want to buy or loan from an auto parts store a fuel pressure tester. You can Tee it in at the firewall. If you have good pressure, the problem is after the pressure gauge. If pressure is low, it's before the gauge. Either the control system (to include wiring), or the pump, or a blockage.
If you've bench tested the pump, you can rule that out. Have you check the voltage at the pump
I doubt the resister is bad. The '94 FSM (F-109) details how you check the resister (and other things). Some people have bypassed the low speed circuit thinking hi speed all the time is good. You could try that to rule out the low speed circuit. I'd still start by checking voltage at the pump and also checking the pump connectors to ensure they are not compromised
You may want to buy or loan from an auto parts store a fuel pressure tester. You can Tee it in at the firewall. If you have good pressure, the problem is after the pressure gauge. If pressure is low, it's before the gauge. Either the control system (to include wiring), or the pump, or a blockage.
If you've bench tested the pump, you can rule that out. Have you check the voltage at the pump
I doubt the resister is bad. The '94 FSM (F-109) details how you check the resister (and other things). Some people have bypassed the low speed circuit thinking hi speed all the time is good. You could try that to rule out the low speed circuit. I'd still start by checking voltage at the pump and also checking the pump connectors to ensure they are not compromised
Good luck
So I bought a fuel pressure testers and checked fuel pressure from firewall and got nothing. Checked fuel pressure straight out of housing fuel pump and nothing. Jumped resistor and nothing. Tested voltage on resistor and nothing. Tested fuel pump relay and nothing from top 2 inserts coming from relay panel. Bottom 2 tested 12 v but top 2 tested nothing. I didn't have schematics with me and jumped on my computer right now to double check the relay schematics to see if top 2 are the plunger which is what I'm suspecting since the bottom 2 have 12 V once key turns on. I just wanted to post my findings here first. I will have to trace it back but if I'm not mistaken, before the relay is the ignition then battery. I don't see how my ignition could go bad when I never touched it so I'm thinking its going to trace back to the ECU. I'm goin to guess the ECU will show no voltage to fuel system so I'll have to dig into what can prevent fuel system from not activating. I know on most cars, rpm sensors will cut off fuel for safety reasons but not sure specifics for FD's.
Update: I finally was able to check out the 94 FSM and was able to properly diagnose my fuel control system with actual comparable numbers. I tested the resistance on my resistor and it read 1.2 Ohms. Book says need to be between 0.57 - 0.70 at 20 degrees C which is about 68 degrees F. I live in Hawaii so that's a little lower then our room temperature so I'd assume they wanted me to check it at a decent cold start temperature. I checked my fuel pump relay to be safe and it is operating at the correct numbers. Plunger kicks on when jumped from a 12v and reads at about 0.07 which is pretty close to no resistance if you ask me. I will be ordering the fuel pump relay just in case but I feel the numbers is within specs. Now the issue is finding a resistor. If anyone has a lead, please let me know. I couldn't find any on Ebay or Atkinsrotary.
If you're getting any resistance on that resistor I wouldn't worry about it just yet. Try removing the fuel pump relay and bypassing it. That should eliminate a few variables.
If you think its the resistor try bypassing the speed relay. If the pump turns on then you know its the problem.
If you're getting any resistance on that resistor I wouldn't worry about it just yet. Try removing the fuel pump relay and bypassing it. That should eliminate a few variables.
If you think its the resistor try bypassing the speed relay. If the pump turns on then you know its the problem.
I removed fuel pump relay and jumped with no results. I also tried jumping the fuel pump speed relay and no results. Going to start looking into the ECU diagram to see if its my ECU. I'm out of ideas at this point. I was trying to get it fixed in time before I left Hawaii and head out to NC in about a week. I won't be able to touch the car for about 3 months. Then I'll have another month to get the car up and running or I may never see the car again. This sucks
I removed fuel pump relay and jumped with no results. I also tried jumping the fuel pump speed relay and no results. Going to start looking into the ECU diagram to see if its my ECU. I'm out of ideas at this point. I was trying to get it fixed in time before I left Hawaii and head out to NC in about a week. I won't be able to touch the car for about 3 months. Then I'll have another month to get the car up and running or I may never see the car again. This sucks
Well wait a minute, if you jumped both of those relays at the same time then that means you have a power issue, or a ground issue. With the FP relay and the Speed relay both jumped, you should have 12v to the FP. Run this wire back.should take you 15 minutes. Make sure the key is in the run position.
Well wait a minute, if you jumped both of those relays at the same time then that means you have a power issue, or a ground issue. With the FP relay and the Speed relay both jumped, you should have 12v to the FP. Run this wire back.should take you 15 minutes. Make sure the key is in the run position.
1,2 & 3 checked out good. I had a hard time finding #4 so I tried number 5 and the voltage was funky. I pulled out the ignition wire to test the plug side and first of all, someone spliced the ignition in order to install a greddy turbo timer. I tested all wires just to see what they would give me but the blue/green wire coming from ignition switch was reading 10v. 2 other wires was reading 12 v but I checked it a second time because I was looking at how the wires were ran with the splicing and I got 0v to all terminals from the same ignition plug. I have to take a look at it tomorrow when I work on it again. Honestly trying to decipher the schematics was a little challenging for me. I' assuming #4 comes out of the fuse box and 5 looks like its in the actual ignition, so I gotta open up the ignition or am I testing the correct plug that goes into the ignition? I figure its the B/G wire since its the closest to #5. Forgive me for being a retard to these schematics. Schematics is all self taught.
OK, If you have power at number 1 then you dont need to check the other ones. So you have power to the fp relay but when you jump it and the speed relay the fuel pump doesnt kick on? It should, unless you have a bad fuel pump ground.
And my bad about number 4, thats not a connector.
And 5 is on the back of the ignition switch, where all the wires go to it.
OK, If you have power at number 1 then you dont need to check the other ones. So you have power to the fp relay but when you jump it and the speed relay the fuel pump doesnt kick on? It should, unless you have a bad fuel pump ground.
And my bad about number 4, thats not a connector.
And 5 is on the back of the ignition switch, where all the wires go to it.
But where would the fuel pump ground be? It sits in the tank and connects to a positive negative coming out of the housing. From the housing plugs into the fuel pump plug. I don't have an external ground anywhere besides the cover but I was told that is for the low level ground and the housing is clean. I even accidentally sparked that ground when I tried straight jumping the fuel pump from the battery. Didn't work by the way. I think my 3 switch was wired incorrectly so I gave up on that. I guess I'll have to just trace the wire manually to see where the ground is. Also I jumped both at the same time and car still didn't start. I have my fuel pressure gauge hooked up and still reading zero.
But where would the fuel pump ground be? It sits in the tank and connects to a positive negative coming out of the housing. From the housing plugs into the fuel pump plug. I don't have an external ground anywhere besides the cover but I was told that is for the low level ground and the housing is clean. I even accidentally sparked that ground when I tried straight jumping the fuel pump from the battery. Didn't work by the way. I think my 3 switch was wired incorrectly so I gave up on that. I guess I'll have to just trace the wire manually to see where the ground is. Also I jumped both at the same time and car still didn't start. I have my fuel pressure gauge hooked up and still reading zero.
One way you can confirm before you start chasing the ground wire is to jump the FP and Speed relay again and check for 12v at the fuel pump. If you have 12v the only missing link would be a ground.
The FP ground looks like it runs back into a dedicated ground in the rear harness.
You can also check the ground at the fuel pump by setting your volt meter to the continuity check. Put one probe on the FP ground and one probe on a bare piece of metal on the car. Should have 2ohms or less resistance.
One way you can confirm before you start chasing the ground wire is to jump the FP and Speed relay again and check for 12v at the fuel pump. If you have 12v the only missing link would be a ground.
I'll try it in the morning. Thanks for the help bro. Giving me hope now.
Not sure it's related, but if it was me i would remove the turbo timer (and check the connections for any melting). They've been known to cause electrical issues and i really don't think they provide any benefit (just run your car a little at vacuum vice boost before shutting down)
One way you can confirm before you start chasing the ground wire is to jump the FP and Speed relay again and check for 12v at the fuel pump. If you have 12v the only missing link would be a ground.
The FP ground looks like it runs back into a dedicated ground in the rear harness.
You can also check the ground at the fuel pump by setting your volt meter to the continuity check. Put one probe on the FP ground and one probe on a bare piece of metal on the car. Should have 2ohms or less resistance.
so I jumped fuel pump relay and fuel speed relay and tested voltage from positive terminal to ground on car and got 12v. For the hell of it, I pulled the fuel pump out of tank still attached to housing and hooked up terminals. My intent was to check 12v to pump and as soon as I turned the key on, the fuel pump turned on. Put the pump back in tank and still nothing. Could it be I have a fuel pressure leak someplace? I did take out my fuel injectors and replaced all seals and diffusers. Only the primaries because I didn’t want to take off the LIM to get the secondary diffusers out. I did change out the fuel filter but I bought a cheap one. But after a few cranks I pulled the main fuel line from fuel pump housing and no fuel. Shouldn’t the fuel at least feed through that line to the filtering the filter was bad?
Not sure it's related, but if it was me i would remove the turbo timer (and check the connections for any melting). They've been known to cause electrical issues and i really don't think they provide any benefit (just run your car a little at vacuum vice boost before shutting down)
I actually checked out the turbo timer harness to see if it had any melt downs and didn’t find anything. I actually don’t need it anymore because I put in an aftermarket alarm system that has a built in timer
Almost sounds like you have your fuel line setup incorrect. Can you double check? Fuel filter on backwards?
When you say you pulled the main fuel line from the fuel pump do you mean on top of the hat? Can you try jumping 12v directly to the fuel pump while its in the tank and try starting it?
The fact that the pump runs out of the tank but not in the tank under the same circumstances doesnt compute. Are you sure its not running, or could you not be hearing it?
If the fuel pump outlet is blocked somewhere, it could just be pressurizing to its max pressure and shutting off.
Almost sounds like you have your fuel line setup incorrect. Can you double check?
When you say you pulled the main fuel line from the fuel pump do you mean on top of the hat? Can you try jumping 12v directly to the fuel pump while its in the tank and try starting it?
1st photo is now and second photo is what it was before I took anything apart.
09-16-20, 11:38 PM
