626 fails to start when hot. dealer perplexed.
 

Hi there. I see that there are a lot of knowledgeable people on this forum so I figured I'd ask my question here!

I've got a 2001 4cyl mazda 626 with 88k miles. For the past year the vehicle has intermittently failed to start in warm weather, generally when the vehicle has been running for a while, shut off, and [attempted to be] started again, anywhere from just a couple mins to 45 mins after it was shut off. It performed flawlessly in less than 50 degree farenheit weather [didn't have a single problem all winter long], but once it got warm again, the problem returned.

What happens when I try to start the car is that it will fire a few times, sounding like it's going to start. Sputter a bit then die. I can try a couple more times, get a few sputters, then nothing but dry cranking. And after a few attempts all I get is starter rotation with no ignition.

It almost* always starts when it's been off for an hour or two or longer.

So far I have taken the vehicle to 4 different shops including two mazda dealerships but to no avail. None were able to reproduce or troubleshoot the problem since it is intermittent and never occurred while the car was in the shop.

Here is what I have replaced so far since the problem began:
Plugs
Wires
Battery
Fuel Filter
Fuel Pressure Regulator (x2)
Fuel tank sensors of some sort. I wasn't involved in this repair so I don't know exactly what was replaced, but it had no affect on the problem.

One potentially valuable piece of information is that the fuel pressure regulator has gone bad twice in two years. So I can only suspect that something else in the vehicle is my problem, and causing the pressure regulator to fail. Could anyone tell me what components could possibly cause damage to this part? Any ideas what else could be wrong?

thank you.

RE: 626 fails to start when hot. dealer perplexed.
 

It sounds pretty much like you do have a fuel related problem. If the plugs or injectors were not firing then you would not even get the sputter. The only thing I could really think of that would cause repeated damage to the fuel pressure regulator was continued very high fuel pressure to it. What was the reason for failure and replacement or were you told?
Fuel pump would be the most suspect due to the recurrance of regulator failure but is an expensive first guess. I think that I would either try to replace the fuel pump relay or swap it with some other relay as a first trial. The relay is located in the underdash fuse/relay box near the battery. Relays should be label and mapped on the top or underside of the cover. Should be labeled either FUEL or more probably CIRCUIT. The horn relay should be located just opposite. I am fairly sure that they are the same relay. If they look the same they are. You could try to swap and see what happens from there.
Have you tried to remove the fuel line to the regulator when it will not start to see if you have any fuel pressure/flow?

RE: 626 fails to start when hot. dealer perplexed.
 

thanks a lot for your reply. I'm not opposed to putting money into trouble shooting at this point....since no-one seems able to pinpoint the problem, and I wish to get it fixed..so I'm probably going to try the fuel pump next (yours wasn't the only opinion that it could possibly be the pump, you just encouraged that as a possibility :D)

ok I took at look at the relays. there are six on my vehicle in the fuse box housing. two different types.

type 1:
H/L Relay
Horn Relay
Air Con Relay
TNS Relay

type 2:
EGI Main relay
Circuit Relay.

So I'm guessing the EGI relay is related to the fuel system, and the relay you were speaking of? or the Cicruit relay? or both? unfortunately neither of those are the same as the horn relay, so I can't follow that advice I'm afraid.

The mechanics who replaced the FPR only said "you have a bad fuel pressure regulator", nothing more specific or in depth as far as an explanation goes. and no I haven't tried disconnecting the fuel supply to the FPR when it's not starting. should I do that and crank the engine to see if fuel comes out? actually I seem to remember one mechanic/friend of mine doing this when the car WAS running, and not getting any fuel to come through...then he said something to the effect of "god I'm an idiot, this is a reverse flow fuel system"...although I didn't know what that really meant.

I tried calling mazda today to check on prices of relays but they were closed for the weekend. would it be reasonable to replace both the Main Circuit and EGI relays as a trouble shooting step? do you have a rough idea of approximately how much these cost?

thank you!

RE: 626 fails to start when hot. dealer perplexed.
 

I just thought I'd give an update of information based on the last time my car failed to start. it was hot and humid out, so one of those two things is causing the lack of a running vehicle.

when I first tried to start the car the engine made a sort of gurgling noise. it fired once or twice, gurgled a bit, then killed. I was able to do this a few times and finally there was no ignition at all...just dry cranking. finally about an hour and a half later after trying every 20 minutes or so to start the vehicle it fired right up, and I smelled gas REALLY strong right after it started. so I suspect I flooded the engine in my attempts to start the car, which MIGHT mean the problem I'm having is too much fuel, as opposed to not enough.

so at this point I'm thinking the issue is either improper fuel supply (which would be what, bad fuel pump? bad 'computer'?) [most likely too much* fuel as the fuel pressure regulator keeps failing]; or improper timing between the fuel supply, crank position and ignition pack/spark plug. (the reason being if the spark is igniting the gasoline when the piston is in the wrong position I would get a weak rotation/firing correct? I'm hypothesizing here). [could the problem be a bad crank positioning sensor? would that cause weak firing on engine start?]

any input is much appreciated.

RE: 626 fails to start when hot. dealer perplexed.
 

another trouble shooting question, this one should be more basic.

if my fuel pump is pumping through too much fuel, could that flood the engine? or would the fuel injectors only inject the proper amount of fuel regardless of what the fuel pump is putting out?

thanks.

RE: 626 fails to start when hot. dealer perplexed.
 

Take a look and see if any of your fuel lines are routed near the exhaust. It sounds like vapor lock to me. The lines can get excessively hot and essentially boil the gas. This won't allow the gas to flow properly through the system.

RE: 626 fails to start when hot. dealer perplexed.
 

sounds like fuel vaporisation to me mate, if its only when its hot

RE: 626 fails to start when hot. dealer perplexed.
 

Interesting that I found a problem similar to the same issue I am having with my 2000 Mazda 626, 4 cylinder. My Mazda has only 70,000 miles on it, however I just started having the same kinda problem that you seem to have had with your Mazda. And yes, my Mazda 626's problem is also intermittent- very frustrating,since my car has not wanted to start twice now after the car is warm or I can finally get it started but then it idles real rough and dies immediately.

So this last time I had the same problem I hadmyMazdatowed into the shop so my mechanic could possibly get the code to determine what is the problem. However, my car showed no codes and that all systemswere okay. My mechanic thinks possibly it is the fuel pump regulator, but we have not gone as far to replace it.

What was determined with your Mazda? Did you ever get the problem fixed?

Does anyone knowif the fuel pump or fuel pump regulator is in the gas tank on the 2000 Mazda 626? [:-]

What is the cost to have fuel pump and/or the fuel pump regulator replaced?

RE: 626 fails to start when hot. dealer perplexed.
 

Take a look at link to the following Mazda TSB. I know it says for cold start in the bulletin but could also still apply to your 626.

http://www.mstore2000.com/PDF_Files/01-027-04-1254.pdf

RE: 626 fails to start when hot. dealer perplexed.
 

Thanks for the information on the problem with my Mazda 626. Believe it or not, I am still having the same intermittent problem. [:@]Frustrating!!!! My Mazda would never show a code so my mechanic could fix the problem. So my mechanic suggested that I drive my vehicle until I get a code.

Since March 2007, my check engine light has flashed on briefly, but would go back off very quickly. After several trips to my mechanic, he was stillunable to diagnose the problem.

Luckily, this morning my check engine light came on and stayed onwhen my Mazda was hestitating after take off from a stop. So I immediately took my car back to my mechanic in hopes he could diagnose the problem. The code read a misfire. I told my mechanic to keep my car to look at it further so maybe he can finally correct this problem (I hope). I will give a copy of this Service Bullentin to my mechanic to see if this helps solve this issue. [&:]