hot start issues, another possibility
10-20-13, 01:13 PM
#1
hot start issues, another possibility
in recent years i have noticed quite a few pressure regulators with ripped diaphragms, i just figured i would make a note of this since it is also going to be a major contributor to flooding/hard starting issues. the diaphragm on my TII is starting to leak so i figured now is as good of a time as any to mention this growing problem.
if you have hard starting issues when hot and compression tests fine, warm up the car and let it sit for a few minutes. remove the port hose from the regulator and run your finger under the metal nipple, if you have a leak it should show up by either dripping from the port or minor residue on your finger if it is just beginning to fail.
higher boost pressures and higher fuel pressure from say a walbro tend to cause them to fail quicker.
the problem isn't noted in irregular fuel pressures but in the fact that raw fuel is dumped into the intake runner after shutting the car off. it only takes a few seconds to rule out for your hot start problems.
if you have hard starting issues when hot and compression tests fine, warm up the car and let it sit for a few minutes. remove the port hose from the regulator and run your finger under the metal nipple, if you have a leak it should show up by either dripping from the port or minor residue on your finger if it is just beginning to fail.
higher boost pressures and higher fuel pressure from say a walbro tend to cause them to fail quicker.
the problem isn't noted in irregular fuel pressures but in the fact that raw fuel is dumped into the intake runner after shutting the car off. it only takes a few seconds to rule out for your hot start problems.
Last edited by RotaryEvolution; 10-20-13 at 01:16 PM.
Trending Topics
10-29-13, 10:50 AM
#8
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,802
Received 2,577 Likes
on
1,831 Posts
after thinking about this for a while i think a bad fuel pressure regulator could actually be a possibility.
ive seen a couple catastrophically fail, where the diaphragm fails and it actually leaks, but i have to wonder if they don't get stuck/fail in a different way too.
and of course there is another thing to be aware of. Higgi was showing me some datalogs of his car, and he was logging fuel pressure and you can clearly see the fuel pressure regulator top out @10psi
ive seen a couple catastrophically fail, where the diaphragm fails and it actually leaks, but i have to wonder if they don't get stuck/fail in a different way too.
and of course there is another thing to be aware of. Higgi was showing me some datalogs of his car, and he was logging fuel pressure and you can clearly see the fuel pressure regulator top out @10psi
10-29-13, 11:48 AM
#9
yep, beyond 10psi the pressure is pushing on the diaphragm which is usually what tears them.
i know for a fact it is more than a possibility as i've diagnosed and repaired some cars with this symptom with a faulty regulator that was a little more extreme than a slow drip.
i know for a fact it is more than a possibility as i've diagnosed and repaired some cars with this symptom with a faulty regulator that was a little more extreme than a slow drip.
10-29-13, 12:38 PM
#11
on the pressure port side not the fuel side.
meaning if you apply 10psi of pressure to the regulator you will get a 10 psi fuel pressure increase, beyond that there is a marginal increase but not linear like it is supposed to be.
basically meaning the regulator is only designed for 10 psi of boost max, beyond that it is stressing the regulator diaphragm and offering no benefit of increased fuel pressure.
a walbro could bandaid this by adding more pressure since statically it adds nearly 10psi of fuel pressure without touching anything but it will not follow the increase in boost beyond 10psi.
meaning if you apply 10psi of pressure to the regulator you will get a 10 psi fuel pressure increase, beyond that there is a marginal increase but not linear like it is supposed to be.
basically meaning the regulator is only designed for 10 psi of boost max, beyond that it is stressing the regulator diaphragm and offering no benefit of increased fuel pressure.
a walbro could bandaid this by adding more pressure since statically it adds nearly 10psi of fuel pressure without touching anything but it will not follow the increase in boost beyond 10psi.
Last edited by RotaryEvolution; 10-29-13 at 12:42 PM.
Thread
Thread Starter
Forum
Replies
Last Post