My car won't start... it cranks but never catches.

[Mike Hughes]

Hi all,

I think I may have a relay problem. I'm not sure which one, though, so please allow me to describe the symptoms.

On the way to work I hit a small pothole and my car lost power. I coasted to a stop and re-started it and it started and drove okay.

I parked the car at work and then started it fine on my way home. At a stoplight, it died again. I tried restarting, but it wouldn't catch. I turned off the a/c and radio and it started weakly.

A block down the road it lost power again and never was able to start. I had it towed to my apartment because it was too late to get it to a shop.

Here's the symptoms:

Everything electrical in the car seems to work fine. All accessories are behaving as they should be according to the position of the key.

When I turn the key to the 'on' position, I hear a soft click as the check engine light comes on. Then, a second later I hear another soft click-click (two clicks) as the check engine light goes off. I do not hear the fuel pump.

The symptoms (loss of power, intermittent starting) earlier are similar to running out of gas. Does it sound like some kind of fuel pump relay or even the fuel pump itself is out? Does the check engine light going on, then off, suggest that the ECU is still receiving power, so it's not the main relay?

Thanks for any help you can give before I get this thing towed,

Mike Hughes

 

[Sulley]

Sounds like the main relay. Should be under the rear panel behind your right shoulder. Check the online manual if you don't have one.

You can try to hit it. That temporarily (note temporarily) works for some people.
You can take it apart and resolder the connections.
You can get a new one. Easy, quick, and pretty cheap.

There are many threads on the subject.

 

[taqman15]

I agree. sounds like the main relay. I had the same symptoms as you. I would not hear the fuel pump clicking on. I basically kept trying until i heard the fuel pump engage and started the car. I finally replaced the main relay. ever since, no problems at all. I think it was $60 at the dealership and is easy to replace(as mentioned in the post above)

 

[nsxtasy]

Having recently had some experience in this area myself...

The fuel pump runs off the fuel pump relay, and the fuel pump relay runs off the main relay. The main relay is a common failure; the fuel pump relay is not. Bottom line: just replace the main relay. It's easy and cheap, like Sulley mentioned.

You need to pull off the top four-inch bolster across the top of the rear panel behind the seats. Gently pry it off by pulling first from the bottom, then wiggle it off gently.

The ECU is the big metal box behind the passenger seat. Just to the right of it (as you're looking at it) is the main relay, which is labeled with the words "main relay". First, you need to remove the bolt at the top, with a 10 mm socket. Then, there are two connectors that plug into it from underneath, and there isn't a lot of room to grab them. The one on the left is the really tricky one; I found it easiest to use a screwdriver to press on the tab just below the end of the black main relay portion of the connector while gently pulling down on the connector. The one on the right was easy.

 

[Hugh]

Did you run out of gas? Don't laugh, it wouldn't be the first time.

 

[skyguy]

Get one of these. You have a good chance of breaking interior fasteners without it. Any auto parts store, Walmart, etc. has em.

$4.49 at Northern tool.

 

[Veleno]

skyguy,
I was looking for that tool a while back at NAPA and they didn't have it nor did they know what I was talking about! I found one eventually.

 

[drew]

Does the check engine light going on, then off, suggest that the ECU is still receiving power, so it's not the main relay?

The Main Relay (MR) is a COMPLEX relay. It has many contacts and it only takes a failure of one of those contacts to cause problems.

That is why when the MR fails, the fuel pump might work (or not), or the ECU to get power (or not) or anything else the MR powers up (or not) [I'm too lazy to break out the manual for the list].

But suffice to say the exact symptoms of the MR failing is not exactly the same in all circumstances, but in your case it SURE sounds like the MR.

Drew

 

[mfh]

Guys,

Thanks for the advice! I'll be replacing the main relay after the long weekend... everything's closed

p.s. weird, I guess I had an old account on here too.

 

[mfh]

Anyone know which part number I need for my 2000 NSX-T?

Search brought up RZ-0152 for 95+ cars, but thought I would double check.

Thanks!

39400-SL0-003 RELAY (RZ-0101) 2000 Acura NSX 74.60 60.87 Qty:

39400-SL0-A01 RELAY (RZ-0152) 2000 Acura NSX 74.60 60.87 Qty:

 

[Hugh]

39400-SL0-A01 for your 2000 model year.

More info in this thread.

 

[nsxtasy]

Anyone know which part number I need for my 2000 NSX-T?

Search brought up RZ-0152 for 95+ cars, but thought I would double check.

Thanks!

39400-SL0-003 RELAY (RZ-0101) 2000 Acura NSX 74.60 60.87 Qty:

39400-SL0-A01 RELAY (RZ-0152) 2000 Acura NSX 74.60 60.87 Qty:

When you take the top bolster off, and you're looking at the main relay, it says right on it in big letters "MAIN RELAY" and either "RZ-0101" or "RZ-0152".

 

[Hugh]

I'm holding one in my hand as we speak.

MITSUBA
RELAY ASS'Y. MAIN
RZ-0101
JAPAN 12V

It also has a little image that kinda looks like one of the 4 Led Zeppelin ZoSo icons.

 

[Mike Hughes]

I fixed it.

Well, the replacement relay was delayed (UPS sucks these days...), so I decided to fix it myself. I'm going to start this post with some keywords for the db to index so that people with newer cars can will be able to find it in a search.

OBD-2 OBD-II OBD2 OBDII main power relay failure location located cold joint solder newer model behind seat

1. The relay is not between the seats in newer model cars. Looking at the ECU, it's to the LEFT, behind a panel that doesn't seem like it can be removed. Just pull it to the side to access the relay, which is...

2. Mounted BACKWARDS and UPSIDE DOWN (so you can't see the connections or the printed part # info on the unit. However, it's the only thing back there with a giant metal bracket.

3. Use a screwdriver to press the tabs on the two wiring harnesses.

4. To open the box, put a shim between each tab (i used toothpicks.. heh) as you pry them open w/ a screwdriver.. on the 4th tab, pull the whole thing out.

5. If you can, resolder EVERY joint on this crappy through-hole circuit. I can't believe a $90k MSRP car still has a board like this. I saw at LEAST one joint that was visibly broken, and the rest looked *awfully* lame. I did a ghetto job with a radioshack iron, a kitchen sponge, 3-year old radioshack solder, and a plastic screwdriver. It turned out better than OEM quality. That should tell you something.

6. Plug, and play. Whee.

A couple of things to note: For a couple of months before my catastrophic failure, my car had been "fluttering" at idle when I stopped at lights. This started after I got my stiffer aftermarket suspension installed... which leads me to my next point, which is:

The relay is attached rigidly to the car's frame. That means when you hit bumps, it gets shaken hard. My new suspension probably precipitated this failure. If you want to make your relay last longer, let it hang freely or wedge it inbetween some wires or something.

Rigily attaching a poorly soldered through-hole board to a frame that's constantly being jostled..... obviously not a good idea, proven by the huge amount of broken relays.

I'm gonna cut Honda some slack on this one, sicne they probably designed this thing in 1986... but I would definitely recommend EVERYBODY do this repair/upgrade whether or not your car is exhibiting symptoms.

Next up: timing belt/water pump/silicon hoses

I'm gonna take it to the mechanic for that one though

Mike Hughes

 

[kenjrbanga]

My nsx woould not start.
Just replaced the main relay on my 95 nsx and now the car starts without any problems.
I had to take off the passenger curved panel to access the main relay.
Even the dealer had the wrong picture for the location of the main relay for the 95 nsx. Its pictured to the right of the ecu.
How long will this new one last?

 

[davidf]

Many years. FWIW, I'd replace the fuel pump relay as well.

 

[rexnsx]

My 1995 Nsx wouldn't start once in awhile. It will crank but doesn't start. It finally gave out at 100,540 miles. I replaced the main relay on the side of the road in San Diego, Ca. Luckily the Acura dealership down the street had the main relay in stock. It took me 20 mins to do it. I google it on my iPhone It's behind the rear passenger side panel right next to the plugs of the main ECU. I will post pics soon. It started right up with the new relay! I was sooo happy!

 

[usafdarkhorse]

The main relay diagnosis can occasionally be a red herring given the same symptoms.

I've seen more than one ignition switch give the same type of grief. The part costs about the same and is about as easy to swap out if the MR turns out to be fine.

 

[gdae]

I’ve been reading these Broken-Relay-in-the-NSX threads for years, now. I hope there is some crossover to other Honda vehicles, because my DD ’96 Accord is dead in the drive with very similar symptoms.
ASAP I will try to pull the relay and see if that really is the problem. First I have to find it.
:redface:

 

[NSX GT]

The main relay diagnosis can occasionally be a red herring given the same symptoms.

I've seen more than one ignition switch give the same type of grief. The part costs about the same and is about as easy to swap out if the MR turns out to be fine.

Mine does has this issue only when it's warmed up or after a short drive. (It has no problems when its cold) It would crank but not turn over. Sometimes i tap on gas little and then it cranks after the 2nd-3rd try. Does this sound like ignition issue? I just don't want to be stranded. I already changed the main relay a year ago.

 

[TANTO]

Not to be critical of all the excellent posts above. One small comment. The 4" bolster has two metal clips on the bottom and three push clips on the top, so you have to pry it off from the top, not the bottom. You will damage the lower clips if you start at the bottom.

 

[usafdarkhorse]

I’ve been reading these Broken-Relay-in-the-NSX threads for years, now. I hope there is some crossover to other Honda vehicles, because my DD ’96 Accord is dead in the drive with very similar symptoms.
ASAP I will try to pull the relay and see if that really is the problem. First I have to find it.
:redface:

Yes, I've heard of main relay failures for other Hondas as well, but these types of symptoms could point toward multiple components.

Mine does has this issue only when it's warmed up or after a short drive. (It has no problems when its cold) It would crank but not turn over. Sometimes i tap on gas little and then it cranks after the 2nd-3rd try. Does this sound like ignition issue? I just don't want to be stranded. I already changed the main relay a year ago.

Worth a shot?

FWIW, my old NSX would occasionally take about 10 rotations to fire up when warm. After selling it, the new owner had a no-start problem a few months later, ended up switching out the ignition switch, and hasn't had a problem since.
I've known 3 NSX owners now personally who have remedied this situation with a new ignition switch, but it may not always be the culprit.

 

[SFNSXguy]

FYI I've had several other Hondas including a 1987 Accord 3-dr automatic (still have it) and a 1989 Accord 3dr stick -- both had main relay failures. Symptom for both was when hot refused to start for 15-20 min, then would start and run fine.
My NSX (knock wood) has been fine. The NSX relay is easy to replace (see other posts) the Accord relay was easy to remove (just one bolt), but a PITA to replace (up under the driver's side of the dash in a nearly impossible location to get that one bolt started -- Finially figured how to do it... double-sided sticky pad to hold it in place while the bolt was started).