Crank no start have spark no fuel
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
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Turn the key to run and manually open the AFM door. Can you hear the fuel system?
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Fuel pump doesnt turn on when key is on. It gets power just for some reason isn't turning on.
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Originally Posted by FDream808
(Post 12434962)
Fuel pump doesnt turn on when key is on. It gets power just for some reason isn't turning on.
Turn the key to run and manually open the AFM door. Can you hear the fuel system? |
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 |
Originally Posted by FührerTüner
(Post 12434966)
Turn the key to run and manually open the AFM door. Can you hear the fuel system?
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Originally Posted by TomU
(Post 12435016)
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 |
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 |
Originally Posted by TomU
(Post 12435060)
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 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 Good luck |
Originally Posted by TomU
(Post 12435202)
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 |
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.
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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. https://cimg7.ibsrv.net/gimg/www.rx7...a5410da09a.png https://cimg2.ibsrv.net/gimg/www.rx7...42d3048bfe.png |
Originally Posted by FührerTüner
(Post 12435575)
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. https://cimg7.ibsrv.net/gimg/www.rx7...a5410da09a.png https://cimg2.ibsrv.net/gimg/www.rx7...42d3048bfe.png |
Originally Posted by FDream808
(Post 12435729)
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
https://cimg4.ibsrv.net/gimg/www.rx7...b1018553d4.png |
Originally Posted by FührerTüner
(Post 12435740)
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.
https://cimg4.ibsrv.net/gimg/www.rx7...b1018553d4.png |
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. |
Originally Posted by FührerTüner
(Post 12435752)
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. |
Originally Posted by FDream808
(Post 12435754)
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.
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. |
Originally Posted by FührerTüner
(Post 12435756)
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.
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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)
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Originally Posted by FührerTüner
(Post 12435756)
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. |
Originally Posted by TomU
(Post 12435797)
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)
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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. |
Originally Posted by FührerTüner
(Post 12435865)
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? https://cimg6.ibsrv.net/gimg/www.rx7...00a2ff34f.jpeg https://cimg7.ibsrv.net/gimg/www.rx7...998c39139.jpeg |
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