MSD 50's - any problems with high fuel pressure

Blown&Injected

Active Member
Joined
May 31, 2001
Did a few searches but could not find any comment but I thought I had read something about MSD 50's locking up when the FP gets up in psi.

My O2's are dropping to .0xx as the boost comes up but I also have some leaks in my fuel line too :eek: I know I need to fix the leaks but it also seems like my O2 issue started about the time I up'ed the FP.

I am now getting some induction backfire with some throttle on the road or even a quick stab of the throttle in neutral
 
Blown&Injected said:
Did a few searches but could not find any comment but I thought I had read something about MSD 50's locking up when the FP gets up in psi.

My O2's are dropping to .0xx as the boost comes up but I also have some leaks in my fuel line too :eek: I know I need to fix the leaks but it also seems like my O2 issue started about the time I up'ed the FP.

I am now getting some induction backfire with some throttle on the road or even a quick stab of the throttle in neutral

Not much information given????

MSD 50's should be able to handle 70 psi..above that is iffy? So 43psi initial and 27psi should be ok from my experience.

Lets see you have leaking fuel line!........Hmmm "Not Good"
Also problem started when fuel pressure raised.......Sounds more like "Fuel Pump Issue".
Remember raising fuel pressure, escalates load on fuel pump, and pump Volume decreases with pressure.

In any event need to know more about your set-up...but fix fuel leak before car catches on FIRE.
 
Ive been having this problem, but no other GN people seem to know anything about it. We may have the same issue. My car has had MSD 50s for a while now, but lately it has gotten to the point where it does not want to start unless the pressure is lowered when it is hot. It will start no matter what, just has to have the pressure lowered for the injectors to fire, and im not sure why. I figure it is an electrical resistance issue somewhere along the way.

My pump does not prime, and is run off of its own switched circuit. I turn on my pump before starting the car.

Id really like to get to the bottom of this as its a pretty annoying thing to deal with on a daily driver.

Ive been trying to figure this out
 
MSD's may lock up at >50# static fuel pressure. That has nothing to do with the differential fuel pressure cited by Joe, above. Static is hose off, idle fp.

Car may refuse to start, or be hard to start...then run fine after started.
 
That makes perfect sense, i was told something along those lines by some Ford guru's. Thanks for the tip.
 
My O2's often jump into the .oxx's. Ive wondered if this is actually me running into the 1000's (1 volt) with the o2, when I get too rich. I also get induction backfire and have since I installed the 50's. Once Ive been driving for awhile, and shut the motor off, if I start back up, the engine idles very very rough...but it will start, and I dont have any fuel line leaks that I can see.
 
I have heard of this problem but have not encountered it myself with Delphi 75's, which are the same ball and seat style injector.

Under boost conditions the pressure differential on each side of the injector will equalize to your static fuel setting at the injector.

So if your FP is set at 45, and your max boost is 25 your FP in the rail will be 70. But you will have 25 PSI manifold pressure at the tip of the injector. So the injector pressure (not the pressure in the rail) will still be balanced back out to 45 psi pressure.
 
Very interesting information here - thanks!!! :cool:

Yeah Joe, I know I better be fixing the leak but I just had to hear it run. Just put the engine back in after a long rebuild. Since it is totally fresh, I have not hit it hard, just came on the gas enough to see about 3 psi as I climbed a hill in 3rd gear.

I have an internal/external pump set-up. A line from the external to filter was leaking - fixed.
Then found that the external pumpis leaking thru one of the electrical connector posts!!! Just took that pump out of the loop - always kinda wondered about the effeciency of two pumps in series but that sounds like a good question for another thread.

Now I have a medium drip/leak at the fittings where the steel lines meet the flex lines at the front of the car - I replaced one O-ring but the other one looks fine.

Before all the problems showed up I pumped all the fuel, just one gallon, out of the tank on the 2 pumps. It only took about 60 seconds to pump the gallon out of the tank.

Interesting comment about going over 1 volt on the O2's. Because I seem to spend too much time on the low side of the O2's, I do not think I am over rich, car seems lean; the reason I messed with the fuel pressure in the first place. Maybe time for a new O2 sensor too.
 
55's Supposed to be better

Abot 4-5 years ago one of the guru's on the board posted the results of 50's locking up under high pressure, and recommended at that time to go with the 55's (which might've need high impedence drivers). I can't remeber the guys name (been away for a while), but I think his business was servicing and selling fuel injectors and he teseted them himself. HTH
 
Awesome T said:
Abot 4-5 years ago one of the guru's on the board posted the results of 50's locking up under high pressure, and recommended at that time to go with the 55's (which might've need high impedence drivers). I can't remeber the guys name (been away for a while), but I think his business was servicing and selling fuel injectors and he teseted them himself. HTH

Red A. wasn't very fond of the 50's. Much of the problem was that they definitley needed to be flow matched sets, as they came from MFG all over the place on flow. Static flow tests resulted in as low as 46# and 51-52# high.

They do not like very high pressure due to design & being High Impedance coils.

A good flow matched set should not be a problem if initial fuel pressure regulator setting is in the area of 43#to 45#. I have always told people that if you have to set not only 50# Inj, or any other inj at 49# or above...its time to upgrade to larger injectors.

Plenty of fellows running 10's with 50's, with no issues....go figure?

BTW...reason there are no issues with pressure on 75 MSD/Delphi....they are low impedance/peak & hold injectors vs high impedance, saturated type for the 50 MSD/Delphi.

Joe
 
Joe,

I got a set of 50's from you, well, PTE a few years back that were flow matched. I didn't pay any attention to the markings at the time, and don't have the sheet anymore. I never ran the car with them and I am making some changes. Can you bring me up to speed on the inscriptions on them or is it pretty easy to see what is what from one to the other?

I'll put my glasses on this time....
P.S. sorry for the hijack

:cool:
 
Phatman said:
Joe,

I got a set of 50's from you, well, PTE a few years back that were flow matched. I didn't pay any attention to the markings at the time, and don't have the sheet anymore. I never ran the car with them and I am making some changes. Can you bring me up to speed on the inscriptions on them or is it pretty easy to see what is what from one to the other?

I'll put my glasses on this time....
P.S. sorry for the hijack

:cool:

Mike,

Its been awhile to decode all the #'s inscribed,... but the Injectors were normally flowed at 90% duty cycle. So within the markings you should see a pairing of numbers like: i.e. 43...44..45..etc. Example 90% duty cycle of 50# would be 45#....Hope that helps you. This method was used to separate them in bins to sort matched sets.

The rest of the #'s were date, batch etc. codes.

Joe
 
50's

Blown&Injected said:
Did a few searches but could not find any comment but I thought I had read something about MSD 50's locking up when the FP gets up in psi.

My O2's are dropping to .0xx as the boost comes up but I also have some leaks in my fuel line too :eek: I know I need to fix the leaks but it also seems like my O2 issue started about the time I up'ed the FP.

I am now getting some induction backfire with some throttle on the road or even a quick stab of the throttle in neutral
I had nothing but problems with mine,steeped up to 60's no problems at all .
Ed
 
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