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Will you please help me diagnose a no-start issue?

13 April 2012
First time poster here. I do not own an NSX, although I am an admirer; I am trying to help a friend whose car is in the body shop and will not start.

Issue: Motor cranks but does not fire. Battery good, starter good, starter turns, motor turns, but motor won't ignite.

Background: Car is a Sunday driver. Don't know if it is on a battery tender during the week. Well cared for, garaged, maintenance up to date.

Body Shop's hypothesis: Some type of factory alarm system disabled the spark.

Owner's comments: Had the car for 10 years, did not come with a key fob, did not install an aftermarket alarm, is not aware of a kill feature.

I searched the forum and read a number of posts on no-start issues, primarily bad starters, solenoids, even clutch issues.

I am thinking a relay of some sort, maybe a clutch switch.

Will you please offer your perspective? If he doesn't get the car started, it's off to the dealership which is going to cost a few dollars....

Thank you.
It's either no fuel or no spark. Do you have fuel pressure - may be bad fuel pump??? Do you have spark - may be bad ignitor???

You can disconnect the fuel line coming from the fuel filter to the fuel rail, put it inside a gallon jug and have someone turn on the key. The fuel should come out fast, so be careful and tell whoever turns on the key to be ready to turn it off fast. If no pressure check the "Main Relay" on the firewall between the seats (this is the most common failure on these cars).

The "Ignitor" controls the spark to the plugs. Not a common failure but it happens.

Good luck and be sure to post your results here.
If its a honda - most likely a main relay problem
Why was it in the body shop? Was it hit?

but i am thinking main relay also, the hit (presuming its in a body shop for accident) could have "jarred" the insides loose

was any electronics disconnected during the repairs? dashboard come out?
Not sure if the NSX has one(or maybe only later years have them) but many cars have an inertia fuel pump cutoff. If the car is hit hard the switch trips and must be reset before the fuel pump will operate again. Might want to check into that.

If not, it is likely the main relay.
Is the car in question a NSX?
What year is the car? Mileage? Std. or automatic?
Any engine modifications ever made to this vehicle?
What type of repairs? Was welding involved?
Was the battery disconnected while at the shop?
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Also, if it's a '97 or later, make sure you're trying to start it with a factory key. The immobilizer system needs to recognize the chip in the key to start.
Thank you all for your help and opinions.

Here are answers to the questions above:
1. Yes, this is an Acura NSX. I took for granted that I posted to this forum, but recognize that I could have described the car better.
2. Manual transmission, mileage around 70,000, but I'm afraid I don't recall the year. My friend has shared that stats on his car, but it was a while ago..
3. The car is in the body shop for paintless dent removal - a noticeable door ding. Not for anything related to an accident.
4. Modifications include suspension and wheels, but I don't think anything motor related

The owner tells me that he hears the fuel pump prime when the key is switched to the pre-start position. I am leaning towards no-spark versus no-fuel.

Your suggestions regarding main relay may be the culprit.
Also, I will definitely post the results of the repair, as well as full stats. Maybe I can get the owner to share a picture as well.
If it is the main relay, you should be aware that it's an inexpensive part (lists for around $60) and it's easy to replace (just gently lift the interior bolster below the inside window, and you're looking at it).
The owner tells me that he hears the fuel pump prime when the key is switched to the pre-start position. I am leaning towards no-spark versus no-fuel.

This would indicate it is not the main relay. So time to check the ignition system and also check for any connectors loose in the engine bay. There is the ignitor connections. There is a fuel injector resistor in the engine bay, passenger side, near the fan(assuming 1994 or earlier). It has a large gray connector. That would give you no fuel, even if all else is OK.

BTW, Where was the "dent"??