20 replies to this topic

[ChrisA]

What would be the symptoms of a pulsation dampener needing to be replaced, other than it dripping fuel? I'd figure the first dampener would cause the more notible symptoms than the one at the end of the fuel rail. I've noticed some starting problems the recently, where it takes about 4 attempts before it will start. Almost like it is not maintaining fuel pressure. Or may possibly be the underhood pressure regulator is causing trouble or the in tank one. Thoughts?

[Jim Drago]

Chris

Usually the hard start is the first sign of a fuel pump going bad, not pulsation dampner. pulsation dampners rarely fail.  We had the first one fail this year. The fuel pressure gauge started flickering all over the place on dyno.  No idea what was going on there, but we changed the dampner and it went away and acted normally. 

Jim

[ChrisA]

Chris
Usually the hard start is the first sign of a fuel pump going bad, not pulsation dampner. pulsation dampners rarely fail. We had the first one fail this year. The fuel pressure gauge started flickering all over the place on dyno. No idea what was going on there, but we changed the dampner and it went away and acted normally.
Jim

Think the pump is okay. Installed a new Mazda unit about 2-3 years ago.

[Jim Drago]

Think the pump is okay. Installed a new Mazda unit about 2-3 years ago.

 

Unfortunately, we are changing pumps atleast once a year! 99 pumps are not very good at all. With the ethanol in fuel now, they dont last long

Jim

[pat slattery]

You can't even buy the good Mazda pump for a 1.6 from Mazda, you have to buy the cheap replacement

[ChrisA]

Yeah, the '99 unit is a Mitsubishi pump that is also used in such hi-performance vehicles like the Suzuki Sidekick. Well, it is used on some nice sport bikes, too. 

 

That said, the first thing I need to test is adding some fresh fuel. I'm down to about 1-gal of 5-month old gas, so much of volatile properties have probably evaped by now. If fresh gas doesn't fix it, then I'm leaning toward the Dampener or Regulator.

[Jim Drago]

I'm giving 10:1 odds on Fuel pump

[ChrisA]

I'm giving 10:1 odds on Fuel pump

Should it turn out to be the pump, what are the better alternatives, Bosch, Denso? I don't think either are designed to fit the pump hanger cleat properly, although they claim to be direct replacement.

[HoneyBadger - BrianW]

Should it turn out to be the pump, what are the better alternatives, Bosch, Denso? I don't think either are designed to fit the pump hanger cleat properly, although they claim to be direct replacement.

OEM are all that are allowed by the rules.

[Jim Drago]

OEM are all that are allowed by the rules.

It will be OEM and OEM equivalent for 1/1/2014

[SaulSpeedwell]

70% of 99s I see, the fuel pump is fine once started and running, but is below book spec on being able to HOLD pressure once turned off - the rail pressure will just bleed down after you key off - thus the long crank times.  Others are flaky on making enough pressure while running WOT, especially if running MikeCollins.Com special fuel!!!

 

(Ha - funny story, I met Geoff Germane earlier this year, and he said I was the first person he ever met that had actually been subjected to his "Germane" fuel test .... and here I thought the test was named after the word "germane" and not an actual person!!!)

 

Anyway, put a gauge on it and figure out which problem you have.  If long crank times are the ONLY problem, you can probably cheap out for a while. 

[SaulSpeedwell]

P.S.  If your only fuel pump problem is pressure bleed-down at key-off and long crank times, and it holds pressure fine at idle and WOT, just put an inline check valve somewhere between the pump and fuel filter. 

[ChrisA]

P.S.  If your only fuel pump problem is pressure bleed-down at key-off and long crank times, and it holds pressure fine at idle and WOT, just put an inline check valve somewhere between the pump and fuel filter. 

Doesn't the No.1 Dampener act like one? I'm not positive on this regarding the Miata, but according to a friend, it work that way on a Supra.

[AW33COM]

Just buy a fuel pump and swap it.  You're risking damaging the starter eventually.  You can buy a $20 fuel pump as a test and check.  Any good fuel pump is about $60.

[ChrisA]

Just buy a fuel pump and swap it. You're risking damaging the starter eventually. You can buy a $20 fuel pump as a test and check. Any good fuel pump is about $60.

Installed this pump 2-3-yrs ago. It's a new OE unit. Runs fine once started. FPR was added shortly there after and the starting issues a little after that.

[Jim Drago]

Installed this pump 2-3-yrs ago. It's a new OE unit. Runs fine once started. FPR was added shortly there after and the starting issues a little after that.

Chris
You have a fuel pump issue. You can check it above like Mark said or save yourself a lot of hassle and time and change it. If I have seen this failure exactly as you described once, I have seen it literally 20 times. The next thing that will happen is it will be fine and hold pressure until about 5000 rpm( under load) and then your fuel pressure will drop from 50-55 to 30-35, lean the engine and cause engine damage. You mention a new pump from 2-3 years ago like it is "new" now, most change every year as maintenance. We have also put new OEM pumps that were bad from day 1.

Put a gauge on it, it it drops off, it is fuel pump, not pulsation dampner. You need to address or risk engine damage in very near future

[ChrisA]

Chris
You have a fuel pump issue. You can check it above like Mark said or save yourself a lot of hassle and time and change it. If I have seen this failure exactly as you described once, I have seen it literally 20 times. The next thing that will happen is it will be fine and hold pressure until about 5000 rpm( under load) and then your fuel pressure will drop from 50-55 to 30-35, lean the engine and cause engine damage. You mention a new pump from 2-3 years ago like it is "new" now, most change every year as maintenance. We have also put new OEM pumps that were bad from day 1.

Put a gauge on it, it it drops off, it is fuel pump, not pulsation dampner. You need to address or risk engine damage in very near future

Jim, PM sent.

Guess I'll have to get gauge and test it out... Dang car's going to kill me before I even get it back on the track. 

[Mark McCallister]

Should I feel guilty that my '91's fuel pump was installed at the factory when I was still in college, 165,000 miles ago?

[LarryKing]

Guilty? - I would think not.

 

Pissed off when you've worked several laps to advance your position only to have the competitors drive back around you when your car stalls mid-corner - yea, you might feel that.

[SaulSpeedwell]

Chris
You have a fuel pump issue. You can check it above like Mark said or save yourself a lot of hassle and time and change it. If I have seen this failure exactly as you described once, I have seen it literally 20 times. The next thing that will happen is it will be fine and hold pressure until about 5000 rpm( under load) and then your fuel pressure will drop from 50-55 to 30-35, lean the engine and cause engine damage. You mention a new pump from 2-3 years ago like it is "new" now, most change every year as maintenance. We have also put new OEM pumps that were bad from day 1.

Put a gauge on it, it it drops off, it is fuel pump, not pulsation dampner. You need to address or risk engine damage in very near future

 

Yep.  I ran a fuel pressure gauge in my 99, and could never figure out why more people didn't.  If I felt a miss or stumble, I could always glance at it right away and know it was or WAS NOT fuel related. 

 

My 99 cranked slow for maybe a whole season, and then fuel pressure started dropping at sustained WOT load like Jim is saying.

 

The pulsation damper is defnitely not a check valve on these cars  .. when all is working well, the pressure is "trapped" between the pump, the regulator, and the injectors.

 

Maybe fuel pumps are something to look at this winter ....