Hot start problem resolved due to failed check valve in the DMCH fuel pump

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Originally Posted by DeLorean03

Installed mine today. Looks great! Put electrical tape on the clamps to keep the return hose safe from the sharp corners of the injection clamps.

Attachment 22121

Attachment 22122

Didn't fix my cold start issue - was on the fence about it. Fired up absolutely flawlessly after sitting a week. Gave me the typical 3-5 seconds cranking until the engine caught and ran, that was 45 mins after I had the car running for 10 seconds to test the check valve's fuel injection clamps for leaking.

Oh well, Eddie will correct it permanently soon. Now I know that pump is 100% working as it should so the peace of mind is there. We're still utilizing the combo unit for the Megasquirt 3.0 system, so I wanted to know it is working perfectly before sending the car to him.

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What is the new RED Wire all about???
Craig

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Originally Posted by Silverbullet

What is the new RED Wire all about???
Craig

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The red wire is 12 gauge wire ran from the RPM relay to the fuel pump with a 20A inline fuse. Got tired of fuse #7 melting down, so I introduced what I call "Fuse 7A." I run a power wire straight from the battery to the RPM relay, and then another wire from the RPM relay to the fuel pump.

Here is the post and link documenting the vast majority of the work - read up on the rest of the thread in the link here:

http://dmctalk.org/showthread.php?59...ll=1#post84928

So far, Fuse #7 has been cold/to mildly warm (maybe a 3 to 4 on a 1-10 scale of arctic cold to hell fire). It NEVER gets hot now - a lil' warm, yes - but hot = not at all anymore.

My review and installation of the SMC 410 check valve from US Plastics Corp, including photos, can be viewed at DMCToday.com for those interested:

http://www.dmctoday.com/showthread.p...ull=1#post3911

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Originally Posted by DeLorean03

The red wire is 12 gauge wire ran from the RPM relay to the fuel pump with a 20A inline fuse. Got tired of fuse #7 melting down, so I introduced what I call "Fuse 7A." I run a power wire straight from the battery to the RPM relay, and then another wire from the RPM relay to the fuel pump.

Here is the post and link documenting the vast majority of the work - read up on the rest of the thread in the link here:

http://dmctalk.org/showthread.php?59...ll=1#post84928

So far, Fuse #7 has been cold/to mildly warm (maybe a 3 to 4 on a 1-10 scale of arctic cold to hell fire). It NEVER gets hot now - a lil' warm, yes - but hot = not at all anymore.

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A 20 amp fuse should not even feel warm if your pump has the normal 7 amp draw. The relay compartment does get warm if you have the cover on it for a long drive. So is that what you feel (cover was on)? Can you measure the current draw?

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Originally Posted by Bitsyncmaster

A 20 amp fuse should not even feel warm if your pump has the normal 7 amp draw. The relay compartment does get warm if you have the cover on it for a long drive. So is that what you feel (cover was on)? Can you measure the current draw?

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I meant fuse #7. Not Fuse #7A. Fuse #7A is stone cold.

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Originally Posted by DeLorean03

I meant fuse #7. Not Fuse #7A. Fuse #7A is stone cold.

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Good:hihi:

For those interested, I stopped and restarted the car about 6 times today, post external in-line check valve installation, over roughly 160 miles of travel, 5 of which were hot starts, and experienced no starting problems to speak of!

Thus I'm DEFINITELY thinking that the combo unit's internal check valve FAILED (or is possibly just insufficient for the back pressures required by a stock/OEM system) - and keep in mind that according to DMCH, I have the revised combo unit that shouldn't be exhibiting any check valve issues.

This is why I personally recommend adding an external in-line check valve with every installation of the combo unit, regardless of what DMCH says about it. DPI is already doing this to all cars that show up for service with the combo unit installed. And as far as external in-line check valves go for our stock/OEM fuel systems, the best choice is the SMC 410 series solid brass with integrated 5/16" barbs, 302 grade stainless steel internals, and a viton seal. Cracking pressure is 1psi and it will hold a back-pressure up to 500psi, thus not only will it get the job done, but it should last a lifetime as well.

The valve is manufactured by SMC - Specialty Manufacturing Co. out of the metro Twin Cities area of Minnesota.

http://www.specialtymfg.com/

US Plastics Corp, of Lima, Ohio, is the retailer that had the best price on the valve at the time of my purchase/recommendation.

USPC also offers shipping via USPS Priority Mail for the same price (or cheaper) than regular ground. Thus, a purchase of the SMC 410 valve supports American workers at every level of the supply chain from manufacturing to delivery! Again, my total, including shipping, came to $17.46.

http://www.usplastic.com/catalog/item.aspx?itemid=85394

Anyone who would even consider purchasing any of the other external in-line check valves is out of their mind IMHO :tongue2:

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Originally Posted by NightFlyer

For those interested, I stopped and restarted the car about 6 times today, post external in-line check valve installation, over roughly 160 miles of travel, 5 of which were hot starts, and experienced no starting problems to speak of!

Thus I'm DEFINITELY thinking that the combo unit's internal check valve FAILED (or is possibly just insufficient for the back pressures required by a stock/OEM system) - and keep in mind that according to DMCH, I have the revised combo unit that shouldn't be exhibiting any check valve issues.

This is why I personally recommend adding an external in-line check valve with every installation of the combo unit, regardless of what DMCH says about it. DPI is already doing this to all cars that show up for service with the combo unit installed. And as far as external in-line check valves go for our stock/OEM fuel systems, the best choice is the SMC 410 series solid brass with integrated 5/16" barbs, 302 grade stainless steel internals, and a viton seal. Cracking pressure is 1psi and it will hold a back-pressure up to 500psi, thus not only will it get the job done, but it should last a lifetime as well.

The valve is manufactured by SMC - Specialty Manufacturing Co. out of the metro Twin Cities area of Minnesota.

http://www.specialtymfg.com/

US Plastics Corp, of Lima, Ohio, is the retailer that had the best price on the valve at the time of my purchase/recommendation.

USPC also offers shipping via USPS Priority Mail for the same price (or cheaper) than regular ground. Thus, a purchase of the SMC 410 valve supports American workers at every level of the supply chain from manufacturing to delivery! Again, my total, including shipping, came to $17.46.

http://www.usplastic.com/catalog/item.aspx?itemid=85394

Anyone who would even consider purchasing any of the other external in-line check valves is out of their mind IMHO :tongue2:

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FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

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Originally Posted by Silverbullet

FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

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Agreed. I'm still having good luck with the SUR & R valve. Although more expensive I was able to get one very quickly. Incidentally, a quick phone call to SUR&R (1.800.390.3996 (available 8:00 a.m. - 5:00 p.m., U.S. Eastern Standard Time) verified that they are made in the USA.

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Originally Posted by Silverbullet

FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

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That's why he and others have listed multiple other alternatives. Besides, it's only been a week - give the company time to restock. It's probably a "weird lil' item" to suddenly go "out of stock" on.