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#1 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
This information is about changing the crappy CSFI spider to the much better MP spider.
We've all seen them from different companies. GM, AC Delco, BWD etc. They are all manufactured by Standard Motor Products. Here's an example. MP replacement But 2 things I bet you did NOT know is: What pressure they should achieve and that they can NOT achieve that pressure. Since I rebuilt my engine a 1 1/2 yrs ago, I never checked the pressure of system. It has always idled crappy (lets say crappier then before). Last month I installed a gauge and confirmed it's reading with a Snap-on gauge. The unit from the build could not achieve 45 pounds. Now first remember the OEM spec is 60 to 66 pounds. So I first changed the FPR no change. Then changed the fuel pump, no change. So I surmised the only thing it could be was the central fuel block. I ordered a new injector unit and returned the old one for credit. The pressure now was higher but still not spec. New one was still only 48 pounds. I also figured that due to the fact that both units had low pressure, the specification must have changed. Contacted Standard in Virginia and found out the MP spec was 55 to 62 pounds. But these units still could not get there. So an easy mod to the return line and it runs 100 percent better. So if you don't like the way the vehicle idles after the install of the MP unit, pressure is the problem. Now that I've upped the pressure to spec, it idles smooth as silk. Summary for those searching on the internet for information regarding the Vortec MP injector unit. The new pressure spec is 55 to 62 pounds. Chances are good the unit you get can't achieve it. Modification to the return line is the only way to ensure you get the pressure correct. You can either slightly crimp the return line (near the schrader valve is easiest). Or Try this to correct it. fastenal no.68779 since the return line is 5/16 and most do it centers don't carry that size. Fastenal ships to your door in 3 days. I hope this information helps someone. Last edited by speedygonzales; 06-18-2013 at 05:56 PM. |
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#2 |
Registered User
Join Date: Jan 2009
Location: New Orleans, LA
Posts: 702
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
There is no available adjustable pressure regulators on the market? I assume you may have looked but just curious.
Also I wonder if you could have issues with the pulse damper. It's inline on some cars and some it's built into the pump unit itself. Just as the name presumes it smooths out the flow of fuel from the pump since all rotary pumps don't actually deliver a steady flow under pressure. I have seen them become clogged with crap of years of use. I can't remember exactly but can you or did you disconnect the vacuum supply to the regulator when you checked the pressure. Did it go up any? It should have jumped to about 65psi max. Atleast that's the highest I have ever seen one with a stock pump achieve.
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82 Chevy SWB "OrangeAnimal" Lot of Goodies! Sold 93 GMC 1500 "Angry Red" 383 TBI Powered Fun! 300hp/410ft.lbs. 09 Yaris wife's daily. |
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#3 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
There are no adjustable type cause it's under the upper plenum shown here
http://s207.photobucket.com/user/twi...ntake.jpg.html I changed the pump so since nothing changed there, they weren't the problem. Stock spec is 60 to 66 Something else I found out is the pressure drops over night but never gets to 0. So the fuel is always at the rails. |
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#4 |
Registered User
Join Date: Apr 2011
Location: Mustang, Oklahoma
Posts: 2,806
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Good info, I will be removing my intake to see if my engine has the old injectors or the replacement soon. I have a boyds tank with aeromotive pump so I think my pressure should be fine. (In a 67 C10 running 97 Tahoe vortec csfi? engine)
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Dan <---(my name) 67 SWB C10 project "GEORGIA"-59 Brookwood 2dr wag...Next project-03 Tahoe 4x4 5.3 family ride-07 Hondur Accord, commuter car |
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#5 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
The pump makes no difference. The new injector fuel block is lowering the pressure below spec. 55 to 62 PSI. If you replace the injectors with the new style, check the pressure before you fire it up.
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#6 |
driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,725
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Exellent info speedy!!! From what I read, your actually trying to reduce the return line flow rate so as to up the fuel pressure correct?
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
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#7 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Yes, I have pinched the return line to reduce it's size temporarily until I can get a shutoff valve inline. The size is not a common hardware store item and I did not want one of those 1/4 or 1/2 turn ball valves. They would be too hard to dial in the correct pressure.
The one thing that concerns me with the gate valve I did find is if the packing will stand up to fuel and ethanol. |
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#8 |
Countdown Survivor
Join Date: Aug 2007
Location: Bean Station, East Tennessee
Posts: 9,676
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Speedy, not trying to pick hairs here, but going from 35 yrs as a pipefitter, I believe you're linking to a needle valve in your first post, not a gate valve. A needle valve, or preferredly a globe valve, of which you'll probably not find in 5/16, can be used to fairly accurately regulate flow. The gate valve is not really a "fine adjustment" device. Gate valves, and ball valves, are the most common types available.
' type device. 0
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93 Yukon 89 Silverado Z71 SWB Sport 91 K 2500 Silverado "Lobuk-Worktruk" A MAN OF HONOR DOES NOT LIE, CHEAT, OR STEAL, NOR TOLERATE THOSE WHO DO. Gettin' old ain't for sissies. |
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#9 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
So I used the wrong term. Long as it's not a ball valve, it will still give finer adjustment.
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#10 |
Registered User
Join Date: Apr 2013
Location: Knoxville TN
Posts: 1,170
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
99 350 vortec fuel pressure was 58psi w/ OEM spider.
I swapped spiders (see pics) and it runs perfect. Last edited by Rufton; 06-25-2013 at 05:30 PM. |
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#11 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
58 is below spec for OEM. The replacement will be even further away from it's new spec of 55 -62. I would put money on it.
Also I thought mine ran ok until I brought the pressure up to the new spec for the new unit also. |
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#12 |
Registered User
Join Date: Apr 2013
Location: Knoxville TN
Posts: 1,170
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Both spider styles have built in pressure regulator to control injector pressure. Don't follow why spider specified for OEM application would require a restricted return line.
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#13 | ||
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Quote:
Quote:
Second, the replacement MP unit has a lower spec. It is 55 to 62. I checked with Standard. (Standard is the manufacturer contracted by GM). This lower spec for the replacement MP unit is not printed anywhere. Third, 2 different units purchased 1 1/2 years apart could NOT obtain the 55 pounds minimum. Once I brought pressure up to spec, it ran much better. (for those that did not read, I first changed the FPR then I changed the pump). For those that did change to the new style injectors, even if you think it runs ok, check the fuel pressure. I an willing to bet that it does not get to 55 PSI minimum and if the pressure of your unit is upped to spec, it will run even better. That is why I upped the pressure. |
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#14 |
Registered User
Join Date: Apr 2013
Location: Knoxville TN
Posts: 1,170
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
I understand why you crimped your return line, but isn't there is a possibility that something is out of spec on your vehicle? Maybe your fuel supply line pressure differential, amperage available to your pump, or other gremlin has caused a problem specific to your vehicle. It would be nice to see more than one data point.
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#15 |
driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,725
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
You want data points when all he's said is this is his experience, he thinks others will experience the same thing, and that its something worth checking if you do the conversion....
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
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#16 |
Registered User
Join Date: Apr 2013
Location: Knoxville TN
Posts: 1,170
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Re: Unknown facts regarding replacement 1st gen. Vortec MP fuel systems
Everyone likely knows but I'd like to reiterate safety first if decide to splice valve into high pressure fuel line.
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Tags |
csfi, spider, vortec |
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