Converting to MSD atomic EFI

[Blue85]

1. I believe the fuel pump I have is an external pump (pwms?) part # prd30768 that self regulates at 58 psi. Now I think I want to run a return line bc it’ll dump fuel right in the pick up tray which should aid in preventing starvation at super steep angles for prolonged periods of time.. Do I have to run a regulator with a return line? If I ran a factory style fuel pump in the tank, would I need a regulator for a return?

Where does it say that this pump has an internal regulator? It looks just like the MSD 2225 which is typically used with a regulator. There is some mention of MSD atomic being a returnless system, but the regulator may be in the throttle body. Doesn't the kit come with some documentation?

Your sending unit looks like it's set up for an in-tank pump. That's really the best way to do it, so why not?

2. The instruction manual says you shouldn’t use hard lines and recommends running soft efi rated hose. To me I can’t see why it would be a problem if I had soft hose at the tank and tbi unit with factory hardline in between?

The general factory approach is hardline along the frame, but soft hose to the tank and engine. This allows for movement of the engine and frame flex and reduces noise transfer. Running the entire thing out of rubber hose is usually not recommended.

3. Is there an alternative o2 sensor I could use? The MSD branded sensors cost about $130-$150, but I can’t find any specs on it to try and find a suitable alternative. For example if I had to replace it would there be one I could go get from a parts store?

The sensor is expensive because it's a wideband, but that sounds like they're marking up quite a bit. Do some research because most of the aftermarket setups are using the Bosch LSU 4.2 or 4.9 sensors. One example is Bosch 0 258 007 057 (VW Number: 021-906-262-B). There are a lot of variants that differ just by harness length or mounting accessories.

Here's a bunch on rock auto https://www.rockauto.com/en/partsearch/?mfr=BOSCH&partnum=17***

This site claims that it's using the 17025 (LSU 4.9): https://www.efisystempro.com/wbo2-sensor-sniper-tbi-554-155#tab-description.

What Is The Difference Between The Holley and Bosch Sensor Options?​

As far as a sensor goes, absolutely nothing. 100% identical. As far as packaging goes, one comes in a Bosch box, the other in a Holley package. As far as warranty goes, Holley products are covered by a 90-day warranty against defect in material or workmanship. The ones in the Bosch box come without warranty.

That makes sense since that sensor is also used with a lot of WBO2 gauges. https://www.rockauto.com/en/parts/bosch,17025,oxygen+(o2)+sensor,5132 That's a "universal" part, but if you can figure out a suitable harness length, you could find an OE application that works on your install. Look here: https://rusefi.com/forum/viewtopic.php?t=1478

 

[HawK5]

Well I called MSD and got some answers, regardless of what pump you run, if you have a return it has to have regulator, they say you can not have any hardline as the pulsing from the injectors can cause cavitation, and they gave me a Bosch part # 17018 which is only like $50-$60.. the advantage of the pwm pump is it doesn’t require a return, but I’ve reached the conclusion it’s a necessity with my intended use.

 

[Blue85]

you can not have any hardline as the pulsing from the injectors can cause cavitation

Oh no! Every car maker in the world has it wrong. Everybody sell your stuff before cavitation takes it out and go Amish!

 

[JoshHefnerX]

You can always go to a fuel cell w/ a bladder - that will keep the pump fed. Just like aircraft!

 

[HawK5]

Oh no! Every car maker in the world has it wrong. Everybody sell your stuff before cavitation takes it out and go Amish!

Hahahaha, yeah I highly doubt it too, but at this point to adapt my existing hardline and find a place for the fuel filter, plus source a hard return line, I’m thinking maybe I just run soft both ways.. I’m kind of trying to prevent any issues and questioning if I should be done something they way they recommend..

 

[dyeager535]

Hahahaha, yeah I highly doubt it too, but at this point to adapt my existing hardline and find a place for the fuel filter, plus source a hard return line, I’m thinking maybe I just run soft both ways.. I’m kind of trying to prevent any issues and questioning if I should be done something they way they recommend..

I struggle with being the safety police on this one, but to me, running decent pressure in soft line is something to be done for short periods, if at all.

GM didn't run soft line even at 13PSI if it was underneath a crew compartment. TBI K5's and suburbans had no soft line (yes, they did use braided sections to account for vibration, but those were lined with teflon) and used o-ring fittings, trucks had soft line/clamps only at the sending unit.

Maybe there is some miracle rubber nowadays that is impervious to ozone, heat, pressure, abrasion, and chemicals, but I kind of doubt it. I've seen enough rubber line that has abraded even against perfectly flat surfaces to trust my truck to rubber line containing 40+PSI of fuel. Rubber line is so flexible that it WILL abrade because you simply can't clamp it enough (feasibly) to eliminate it's movement.

The plastic line used on newer vehicles at this stage are probably a potential option, but personally I don't think I like it either, for a retrofit.

As always, people are free to do what they want with their trucks. But vehicle fires are almost always related to people doing dumb things with fuel delivery, and are thus preventable. I prefer to stick within the margin of safety the manufacturer built the system with.

 

[HawK5]

I struggle with being the safety police on this one, but to me, running decent pressure in soft line is something to be done for short periods, if at all.

GM didn't run soft line even at 13PSI if it was underneath a crew compartment. TBI K5's and suburbans had no soft line (yes, they did use braided sections to account for vibration, but those were lined with teflon) and used o-ring fittings, trucks had soft line/clamps only at the sending unit.

Maybe there is some miracle rubber nowadays that is impervious to ozone, heat, pressure, abrasion, and chemicals, but I kind of doubt it. I've seen enough rubber line that has abraded even against perfectly flat surfaces to trust my truck to rubber line containing 40+PSI of fuel. Rubber line is so flexible that it WILL abrade because you simply can't clamp it enough (feasibly) to eliminate it's movement.

The plastic line used on newer vehicles at this stage are probably a potential option, but personally I don't think I like it either, for a retrofit.

As always, people are free to do what they want with their trucks. But vehicle fires are almost always related to people doing dumb things with fuel delivery, and are thus preventable. I prefer to stick within the margin of safety the manufacturer built the system with.

You make valid points, I’m kind of surprised a company as big as Holley that owns MSD would sign off on these installation instructions..
Maybe some braided sheathing would be the proper happy medium

 

[dyeager535]

You make valid points, I’m kind of surprised a company as big as Holley that owns MSD would sign off on these installation instructions..
Maybe some braided sheathing would be the proper happy medium

Problem with braided is that you have no idea what is underneath the braiding. It could be cracked and ready to split at any time, you'd have no clue.

Yes, the armor helps, but unless it's lined hose (like OEM) abrasion is the only thing it helps with.

Nicop line or whatever it is called, I believe is fine for fuel and from everything I've read and heard, is easy to form and flare. I don't want to use adapters so when I re-do my hard lines I'm going to get a hydraulic flaring tool that will do the GM Saginaw o-ring "flare".

The -AN adapters to GM Saginaw are often recommended when using early GM fuel injection components, I believe both because they are common and thus not crazy expensive, and they don't use a very uncommon flare requiring relatively expensive tools to make.

 

[6872xtc]

I understand and agree with @dyeager535 about everything concerning what the OEM uses for fuel lines and why.
I also know how many decades manufacturers of semi trucks have been using hoses for fuel feed and return. Completely plastic ones as well as reinforced rubber.
And since the change to common rail fuel feed, the fuel temperatures are up due to circulation through the cylinder head.
So I am less concerned about using a good quality hose.

I don't really understand the view of MSD preferring to use hose, either.

 

[dyeager535]

I also know how many decades manufacturers of semi trucks have been using hoses for fuel feed and return. Completely plastic ones as well as reinforced rubber.

Perhaps that's a good place to start then? What do they spec for fuel hose? I know nothing of those systems, what do they run for pressure?

As long as pressure was the same or greater, and the hose is rated for ethanol, if it's just ran and clamped in a few spots from factory, in rigs that see probably 500k-over a million miles, I expect the OEM's know better than I.

 

[6872xtc]

Perhaps that's a good place to start then? What do they spec for fuel hose? I know nothing of those systems, what do they run for pressure?

As long as pressure was the same or greater, and the hose is rated for ethanol, if it's just ran and clamped in a few spots from factory, in rigs that see probably 500k-over a million miles, I expect the OEM's know better than I.

The feed side hasn't had pressure until Cummins decided to start using an electric lift pump, which still shouldn't be much pressure. My perspective is that I have been around many trucks that have put on a million miles, and we have had dump trucks have 500K, as well as several mixer trucks with 250K on them. With the mixer trucks, that usually means over 30K hours. There are a couple which are over 33K hours. And with the rubber pad suspension and heavy ratings on the axles, they shake like crazy over the road and bumps.
I don’t see failures.
Yes, I understand that pressure adds to the wear of the system, I just don't feel as wary about using quality hose in some situations due to my experience.

 

[AZ79K5Project]

MSD probably knows there product and how their injectors react to hard lines where the GM knows their product and comparing the two may lead to unintended consequences.

I had issues with hard lines with my Atomic 1.

 

[dyeager535]

Yes, I understand that pressure adds to the wear of the system, I just don't feel as wary about using quality hose in some situations due to my experience.

I doubt any quality EFI hose is going to be taxed by common fuel system pressures, my concern is more with splits on fuel hose that is under pressure.

FWIW I've seen GM flexible fuel line sections that had what I presume are called pulse dampeners or similar, perhaps those are used for the reason MSD suggests hose?

 

[Fastereddie]

The feed side hasn't had pressure until Cummins decided to start using an electric lift pump, which still shouldn't be much pressure. My perspective is that I have been around many trucks that have put on a million miles, and we have had dump trucks have 500K, as well as several mixer trucks with 250K on them. With the mixer trucks, that usually means over 30K hours. There are a couple which are over 33K hours. And with the rubber pad suspension and heavy ratings on the axles, they shake like crazy over the road and bumps.
I don’t see failures.
Yes, I understand that pressure adds to the wear of the system, I just don't feel as wary about using quality hose in some situations due to my experience.

Agreed, but diesel fuel seems to be easier if not a preservative on the hoses.
And the stuff the oem’s use is way better than any crap you get at autozone. One definitly has to do some searching to get the good stuff.

 

[6872xtc]

Agreed, but diesel fuel seems to be easier if not a preservative on the hoses.

Yes, kind of. I have found more than a few hoses cooked to the point of being completely stiff. You don't realize it until you have to disconnect one. Rubber and plastic.
But I am still talking about lots of hours on them.
And there have been several trucks with plastic lines out in the sun on top of the tanks.

 

[HawK5]

Yeah Idk very much about efi, and pulsing etc, I just know what they recommend.. My goal is to take my time and collect the right parts so when it comes time to install it I don’t have any additional variables or question marks if something doesn’t work right..