Help Car Won't Start!

[Re<<1]

A quick run down. I have a 98 NSX with 40K miles, car sat for roughly 10 days. Went to start it, engine turned over then immediately died, NO CEL. Now it cranks but engine won't fire. I can hear 2 clicks from main relay then a 3rd. Doesn't sound as if the fuel pump is priming but never really noticed a priming noise to begin with. Battery is steadily at 12.3V. So far I've swapped the main relay and tried paper clip trick with fuel pump resistor and nothing. Car doesn't have an aftermarket alarm. Little black button is still in place behind clutch pedal. Will check to see if fuel pump is getting power later today. Any other suggestions?

 

[jwmelvin]

Dashboard lights on when key on? (May be worth cleaning ignition switch.)

 

[Old Guy]

Three clicks from the main relay would be normal. Fist click when you turn the key to run, second fast click when the relay turns the pump on to prime the system and third click a couple of seconds later when the relay turns the pump off.

The first test is to listen for the fuel pump priming. This may not be so easy. On my car, if the gas tank is anywhere close to full the fuel does an excellent job of damping the vibration from the pump (perhaps I have a really quiet pump). I don't really notice any pump noise in the car. I have read posts on Prime where owners described having to be outside the car and listen down by the left rear wheel while somebody turned the key in order to hear the OEM pump prime.

Whether or not the fuel pump primes will send you on two separate diagnostic paths. Assuming the pump is not priming, check for voltage at the fuel pump resistor location while somebody is cranking the engine. Measure the voltage between the black / red wire at the resistor plug and ground. This is the supply to the fuel pump.




If you are getting 12 volts at this point and the fuel pump is not running. short of a broken wire leading to the pump it pretty much leaves you with the conclusion that your pump has failed.

 

[solidol]

Can't be ignition switch since starter is cranking. Unlikely to be fuel pump failure since it was running fine just recently (unless super unlucky). I would check fuel relay, all the fuses and recheck all the connectors like on igniter and such. Otherwise it may be good time to install those handy fuel pressure gauges on top of the fuel filter.

Also when you say voltage reads ~12 is it under load or at rest?

 

[Re<<1]

Over the weekend I had a friend try and start the car while I measured the voltage leaving the Main Relay. Once the relay closed there is 12V being sent to the fuel pump.

Grounds checked
Fuse #2 and #5 checked
Fuel Pump resistor checked
Main Relay replaced
12V confirmed being sent to fuel pump.
Injectors were sent out for cleaning and calibration last month.

 

[Old Guy]

12 V on the blk/yel wire out of the main relay kind of points a big finger at the fuel pump. Did you do the 'listen test' to confirm that the pump is not running? A fuel pressure test would also confirm that the pump is not running.

 

[Re<<1]

I replaced the fuel pump today with an oem unit and car still won't start. Removed fuel line from filter to make sure its getting fuel, but nothing. No fuel into fuel filter. So far replaced main relay, fuel pump and checked fuses #2 and #5 . Next I'm going to replace fuel pump relay assy., power (4P) (056700-7330). Any other help?

 

[Old Guy]

I replaced the fuel pump today with an oem unit and car still won't start. Removed fuel line from filter to make sure its getting fuel, but nothing. No fuel into fuel filter. So far replaced main relay, fuel pump and checked fuses #2 and #5 . Next I'm going to replace fuel pump relay assy., power (4P) (056700-7330). Any other help?

So, something is not hanging together.

You said that you checked and you have 12 volts coming out of the main relay to the fuel pump (that was the blk / yel wire on the main relay).

You said that you checked the fuel pump resistor and it was OK.

If you have 12 volts coming out of the main relay and the resistor is OK, then the pump should run. The only thing the fuel pump relay does is bypass the fuel pump resistor under high engine load. A non operating fuel pump relay will not stop the car from starting. I would not bother with the fuel pump relay (unless the problem is actually a burned relay socket).

In post #3 I suggested that you check for 12volts on the blk/red wire at the fuel pump resistor. Did you do this? If the car does not start, there will only be 12 volts at that point during the couple of seconds when the prime pulse occurs so this needs to be a two person test. One watches the voltmeter and the other switches the ignition key from off to run. If you get the brief 12 volts reading, then the pump should prime. As I also noted in post #3 , if the pump is not priming, then that means the pump is dead or you have a bad connection between the fuel pump resistor and the fuel pump. If you are confident that the fuel pump is good, time to check the wiring.

As an observation, it is infinitely easier to check for voltage to the pump at the blk/red wire at the fuel pump resistor than it is to check at the main relay. Also, checking at the fuel pump resistor confirms that the main relay is working, the fuel pump resistor is OK and the wiring between the main relay and the resistor is OK. 3 for 1 and its easier to do!

 

[ralph cerbone]

I had a similar problem on my 97 in oct 17 , had power to fp res , jump it out still no pump , jumped out fp relay and had power to fp connector behind driver seat at the sending unit rubber boot ,still no pump . Had a friend tap tank from underneath pump came on ,has to be bad pump right ,WRONG . spoke to larry b says pumps very rarely go bad , my friend concurred with larry . Do to torn rotator cuff i could not change pump myself . Called dealer told him what i did and what i found , he concurred with larry . had car towed to dealer ,they did all checks i did but still did not believe pump was bad . I didn't care change pump its 20 yrs old and if it doesn't work well go from there . My car had a radar detector and lo jack system installed at time of sale in 97 , when the installer powered the lo jack back up battery he stripped the power wire to the fuel pump and wrapped his wires around it ,there where only a few strands of the factory wire left so even when i sent power to the pump it checked ok but had to open when pump was connected . go directly to pump gauge conn. behind seat and then supply power.






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[Re<<1]

So, something is not hanging together.

You said that you checked and you have 12 volts coming out of the main relay to the fuel pump (that was the blk / yel wire on the main relay).

You said that you checked the fuel pump resistor and it was OK.

If you have 12 volts coming out of the main relay and the resistor is OK, then the pump should run. The only thing the fuel pump relay does is bypass the fuel pump resistor under high engine load. A non operating fuel pump relay will not stop the car from starting. I would not bother with the fuel pump relay (unless the problem is actually a burned relay socket).

In post #3 I suggested that you check for 12volts on the blk/red wire at the fuel pump resistor. Did you do this? If the car does not start, there will only be 12 volts at that point during the couple of seconds when the prime pulse occurs so this needs to be a two person test. One watches the voltmeter and the other switches the ignition key from off to run. If you get the brief 12 volts reading, then the pump should prime. As I also noted in post #3 , if the pump is not priming, then that means the pump is dead or you have a bad connection between the fuel pump resistor and the fuel pump. If you are confident that the fuel pump is good, time to check the wiring.

As an observation, it is infinitely easier to check for voltage to the pump at the blk/red wire at the fuel pump resistor than it is to check at the main relay. Also, checking at the fuel pump resistor confirms that the main relay is working, the fuel pump resistor is OK and the wiring between the main relay and the resistor is OK. 3 for 1 and its easier to do!

Thanks [MENTION=7701]Oldguy[/MENTION], Now since replacing the oem fuel pump and Main Relay assuming human error in the past I'm going to start testing again. I first tried the paper clip trick jumping the fuel pump resister hoping for a start but nothing. I had a friend turn the key from OFF to RUN while I measured voltage at the fuel pump resister and now do not see any voltage. Removed fuel line into fuel filter and I'm not getting fuel. When I removed the rear panels to get to the connectors I noticed this wasn't the first time they were removed. The car does have CTSC with fuel pressure regulator. Next I'm going to check continuity and grounding.

 

[Old Guy]

I had a friend turn the key from OFF to RUN while I measured voltage at the fuel pump resister and now do not see any voltage.

One thing to be aware of if you are using a digital voltmeter for testing. They do not continuously measure the voltage that you are testing. They sample the voltage at regular intervals and display the results. On older digital meters or inexpensive meters the sample interval can be quite long, long enough that you might completely miss the prime pulse to the pump. In this case, the super old school 12 volt test light might be more effective. If you are using a high end digital voltmeter such as a Fluke 115 or similar with a MAX capture, this probably won't be a problem.

 

[goldNSX]

Thanks [MENTION=7701]The car does have CTSC with fuel pressure regulator. Next I'm going to check continuity and grounding.

Of course, it has to be a modified car. :wink:
Tell us more about the CTSC system. Did you install the boost-a-pump electronics from CT?
Do you use an aftermarket ECU or the standard piggy back from CT?

 

[Re<<1]

One thing to be aware of if you are using a digital voltmeter for testing. They do not continuously measure the voltage that you are testing. They sample the voltage at regular intervals and display the results. On older digital meters or inexpensive meters the sample interval can be quite long, long enough that you might completely miss the prime pulse to the pump. In this case, the super old school 12 volt test light might be more effective. If you are using a high end digital voltmeter such as a Fluke 115 or similar with a MAX capture, this probably won't be a problem.

Wow, good catch. I previously checked voltage with a old multimeter and it was reading 0 Volts. Now using a newer multimeter I am showing the 12 volts for a few seconds at the fuel pump resister. I'm running through the trouble shooting check list for the fuel pump system and am currently on pg 11-145, checking continuity between main relay and ECM. I want to be sure I have the right ECM connector A (26P). Is this the very top connector on ecu?

Of course, it has to be a modified car. :wink:
Tell us more about the CTSC system. Did you install the boost-a-pump electronics from CT?
Do you use an aftermarket ECU or the standard piggy back from CT?

The CTSC was installed by a dealer by the previous owner. Car has stock ECU and Comptech little black box wired in.

 

[Old Guy]

I have never had to go digging so I don't know where the A connector is on the case. The service manual does not show the locations; but, there are only two 26 pin plugs on the ECU, A and F. You can differentiate them by the wire count and locations. A has 24 wires (2 vacant pins) and F has 22 wires (4 vacant pins) according to the service manual.

Following the service manual is always a good thing; but, in this case if you have confirmed that you are getting 12 volts at the fuel pump resistor during the prime pulse, I would not be checking for continuity between the resistor back to the main relay or the connection between the main relay and the ECU. In order to get 12 volts at the resistor during the prime pulse, those connections have to be intact. I would be following the suggestion of [MENTION=9834]ralph cerbone[/MENTION] and looking at the connection from the fuel pump resistor down to the fuel pump holder. I normally would give that a low probability of failure (unless somebody messed with it as in [MENTION=9834]ralph cerbone[/MENTION] 's case); but, that is where the evidence seems to be pointing.

You replaced the fuel pump. If you still have the original fuel pump it would be useful to do a bench test on it by applying 12 volts to the connections. If the pump runs, that confirms that it was not the pump in the first place and must be the wiring between the fuel pump resistor and the fuel pump.

While poking around the resistor, carefully examine the connections. The resistor gets very hot. That can lead to connection problems. Check the plugs to make sure that you don't have any wiring deterioration right around the resistor connection.

Out of curiosity, what is the Comptech little black box? Is it the FIC used on later versions or something else? Is it that boost a pump thing that [MENTION=10201]goldNSX[/MENTION] mentioned?

 

[jwmelvin]

Out of curiosity, what is the Comptech little black box? Is it the FIC used on later versions or something else? Is it that boost a pump thing that [MENTION=10201]goldNSX[/MENTION] mentioned?

The little black box is the “ESM” aka electronic signal modifier, which clamps the MAP sensor voltage so the factory ECU doesn’t ever see boost. Fueling is “tuned” with the rising-rate fuel-pressure regulator. And the boost-a-pump aka voltage doubler increases the voltage to the fuel pump so that it may (kind of, for some period of time) supply the ~100 psi requested by the RRFPR.

If using an FIC and larger injectors instead of the RRFPR and BaP, the FIC clamps the MAP voltage so there is no need for the ESM.

 

[Old Guy]

The little black box is the “ESM” aka electronic signal modifier, which clamps the MAP sensor voltage so the factory ECU doesn’t ever see boost. Fueling is “tuned” with the rising-rate fuel-pressure regulator. And the boost-a-pump aka voltage doubler increases the voltage to the fuel pump so that it may (kind of, for some period of time) supply the ~100 psi requested by the RRFPR.

Wow - that truly does seem like a bandage engineered system. Is the voltage doubler module located on the pump side of the fuel pump resistor? If so, that would be a good candidate to check out for failure.

Do you know whether it is a voltage multiplier or a DC-DC inverter? Voltage multiplier circuits (aka charge pumps) are cheaper; but, typically have regulation issues and use electrolytic capacitors and we all know what a wonderful reputation they have. I have never heard of someone using a charge pump to drive an electric motor.

 

[jwmelvin]

Wow - that truly does seem like a bandage engineered system.

I agree. The more I learned about it, the more I hated it. Then, when my engine required work (lifted head, seemingly not as a result of the CTSC fueling but who knows...), I replaced it all with a new pump, injectors, and F/IC.

Is the voltage doubler module located on the pump side of the fuel pump resistor? If so, that would be a good candidate to check out for failure.

Yes, it is just before the pump and uses a pressure switch connected to the intake plenum to tell the voltage doubler to increase voltage when MAP goes above atmospheric.

Do you know whether it is a voltage multiplier or a DC-DC inverter? Voltage multiplier circuits (aka charge pumps) are cheaper; but, typically have regulation issues and use electrolytic capacitors and we all know what a wonderful reputation they have. I have never heard of someone using a charge pump to drive an electric motor.

I'm not sure but they do claim to act as a regulator, so I'm guessing a DC-DC converter. Here is the claimed original device.

 

[goldNSX]

Is the voltage doubler module located on the pump side of the fuel pump resistor? If so, that would be a good candidate to check out for failure.

That's what I mean since #12 . Some people have the voltage doubler installed, some not (or they went with more serious fuel pump - less complexity - less failure rate). The voltage doubler is normally installed right above the fuel pump opening, on the inside of the cabin, next to the TCS module (well, about there). A longer hose routes to the boost switch which is normally mounted next to the fuel pump resistor or former engine fan in the engine bay. As soon as there's even the slightest boost the fuel pump gets more voltage by the unit. To install the voltage booster, you have to cut the wire to the fuel pump and the the fuel pump gets power by the voltage doubler ONLY.

If that's the case you can bypass the voltage doubler for testing reasons and supply the fuel pump directly with 12V and see if the engine starts. If it starts you know where the problem is.

 

[Re<<1]

That's what I mean since #12 . Some people have the voltage doubler installed, some not (or they went with more serious fuel pump - less complexity - less failure rate). The voltage doubler is normally installed right above the fuel pump opening, on the inside of the cabin, next to the TCS module (well, about there). A longer hose routes to the boost switch which is normally mounted next to the fuel pump resistor or former engine fan in the engine bay. As soon as there's even the slightest boost the fuel pump gets more voltage by the unit. To install the voltage booster, you have to cut the wire to the fuel pump and the the fuel pump gets power by the voltage doubler ONLY.


If that's the case you can bypass the voltage doubler for testing reasons and supply the fuel pump directly with 12V and see if the engine starts. If it starts you know where the problem is.

Good news, I bypassed the fuel pump regulator unit (FPRU) or voltage doubler and she's back to life. Looking on the bright side. I replaced my 20 yr old fuel pump and learned more about my nsx, it being my first time dropping the gas tank. Since we now know the problem, I believe i have 3 options. 1.) Send it back to CT for repair (idk if this is possible). 2.) Forced to get an aftermarket ECU and remove the FPRU all together. 3.) Remove CTSC and go back to stock.

 

[goldNSX]

We have a winner! Did you check if the FPRU gets 12 V (no input -> no output)?

1) price? What fuel pump did you install (sorry, I'm too lazy to read)?
2) no
3) no

 

[Old Guy]

An aftermarket ECU is a huge amount of work because of the effort associated with setting up starting, warm-up and idle control. If somebody offers the FIC pre configured for the CTSC that may be a viable option.

At the risk of being obvious, don't go doing the pedal to the metal thing with the FPRU by-passed. Insufficient fuel pressure under boost may result in engine damage associated with running high AFRs at high engine load.

 

[jwmelvin]

I have a voltage doubler I would sell you for pretty cheap if you want it.

 

[Re<<1]

An aftermarket ECU is a huge amount of work because of the effort associated with setting up starting, warm-up and idle control. If somebody offers the FIC pre configured for the CTSC that may be a viable option.

At the risk of being obvious, don't go doing the pedal to the metal thing with the FPRU by-passed. Insufficient fuel pressure under boost may result in engine damage associated with running high AFRs at high engine load.

Yes I only started the car havn't driven it with the FPRU bypassed.

I have a voltage doubler I would sell you for pretty cheap if you want it.

Thanks J, Luckily I was able to source one locally and had the car back on the road Friday right before EibachMeet Philly. Made the 1.5 hr trip there and back without any hiccups. Fantastic drive, much needed :smile: Appreciate all the help from everyone, Love the nsx community.