Mercruiser fuel pump 12-15 psi
06-27-2016, 06:22 PM
#33
Registered
iTrader: (1)
I don't think the stroke length would change the static pressure much, only to the extent of the change in the force created by the spring due to the different compressions.
It would change the volume for sure. So it is possible that would result in lower pressure if the engines requirements exceed the fuel delivery at a given RPM, just like running too small a pump. But that is not exactly predicable. And most likely would do zip at idle.
We did some bench testing on these when we first discovered the problem. If you hold one in your hand you can barely push the pump arm.
I cannot remember the part number with the issue, but it was not a random batch. It was all of them from a new vendor. The PN has since been superceded, the new part seems OK.
It would change the volume for sure. So it is possible that would result in lower pressure if the engines requirements exceed the fuel delivery at a given RPM, just like running too small a pump. But that is not exactly predicable. And most likely would do zip at idle.
We did some bench testing on these when we first discovered the problem. If you hold one in your hand you can barely push the pump arm.
I cannot remember the part number with the issue, but it was not a random batch. It was all of them from a new vendor. The PN has since been superceded, the new part seems OK.
Spring over the diaphragm will determine pressure.
Reducing stroke on the arm will cut volume. So some pinhead(s) at Merc decided to cut volume to cut pressure. Since the spring would require more labor, and they obviously wanted an attempted fix vs sending a fuel pump that works correctly...
Mark, I'll bet $100 the supplier was Airtex. They blow goats, and have cost me lots of money at work. Electric pumps - I haven't touched any of their products since,
06-27-2016, 06:39 PM
#34
Registered
Join Date: Jun 2013
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
06-27-2016, 06:56 PM
#35
Registered
iTrader: (1)
From another site
Bad Mercruiser Fuel Pump
May 14th, 2011, 07:50 PM
I'm not sure if many people had this problem or not, so I'm going to just give a little story here about an experience with a Mercruiser fuel pump. I have a 1993 Mercruiser 5.0LX 305 V-8 230HP. I was having a problem with fuel making its way into the oil. So, I learned that either the fuel pump needed to be replaced, or, the carburetor need to be rebuilt. Both of these parts were original from 1993. So, I replaced the fuel pump thinking that the ethanol in the fuel must have eaten away at the internal parts of the fuel pump. After replacing the pump with a mercruiser pump, the engine wasn't really running right and the carburetor was beginning to flood out. The carburetor is a Rochester quadrajet. So now that this was happening, I decided to rebuild the carb since it was all original. After rebuilding, the flooding problem in the carb was still occuring. I tried replacing the needle and seat and float again in the carb with it still flooding out. Then I purchased a rebuilt Quadrajet from a carb shop and was told that if this carb floods out then there is a problem with the fuel pump, and the quadrajet can only take 4-6 lbs of pressure and anything more than that would force the needle open. So, I replaced the carb and still had it flooding. Now I called Mercruiser to que them in on the situation. After I explained to them what had been going on, they said to try a thicker gasket, part # 27-431861. After this gasket was installed, the flooding did stop. However, a few minutes after running the engine, a ticking noise presented itself. This had to be the rod that pumps the fuel pump slapping against the pump or the cam inside the engine since the pump was now about 3/16 of an inch further out from the block. Now another phone call to Mercruiser to find out that "if after using gasket 27-431861, the flooding does not stop, or a ticking noise occurs, then you must use an aftermarket fuel pump." So, now I bought a Sierra fuel pump, part # 18-7283, bolted it on, and had no problems since. Just thought I would try to spread the word if anyone else was having this problem. Any questions, please dont hesitate to ask!
May 14th, 2011, 07:50 PM
I'm not sure if many people had this problem or not, so I'm going to just give a little story here about an experience with a Mercruiser fuel pump. I have a 1993 Mercruiser 5.0LX 305 V-8 230HP. I was having a problem with fuel making its way into the oil. So, I learned that either the fuel pump needed to be replaced, or, the carburetor need to be rebuilt. Both of these parts were original from 1993. So, I replaced the fuel pump thinking that the ethanol in the fuel must have eaten away at the internal parts of the fuel pump. After replacing the pump with a mercruiser pump, the engine wasn't really running right and the carburetor was beginning to flood out. The carburetor is a Rochester quadrajet. So now that this was happening, I decided to rebuild the carb since it was all original. After rebuilding, the flooding problem in the carb was still occuring. I tried replacing the needle and seat and float again in the carb with it still flooding out. Then I purchased a rebuilt Quadrajet from a carb shop and was told that if this carb floods out then there is a problem with the fuel pump, and the quadrajet can only take 4-6 lbs of pressure and anything more than that would force the needle open. So, I replaced the carb and still had it flooding. Now I called Mercruiser to que them in on the situation. After I explained to them what had been going on, they said to try a thicker gasket, part # 27-431861. After this gasket was installed, the flooding did stop. However, a few minutes after running the engine, a ticking noise presented itself. This had to be the rod that pumps the fuel pump slapping against the pump or the cam inside the engine since the pump was now about 3/16 of an inch further out from the block. Now another phone call to Mercruiser to find out that "if after using gasket 27-431861, the flooding does not stop, or a ticking noise occurs, then you must use an aftermarket fuel pump." So, now I bought a Sierra fuel pump, part # 18-7283, bolted it on, and had no problems since. Just thought I would try to spread the word if anyone else was having this problem. Any questions, please dont hesitate to ask!
06-27-2016, 07:06 PM
#36
Registered
Join Date: Jun 2013
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Yes I have read this thread, however no one offers a mechanical pump for a 90-92 mark iv carbed 502 that I'm aware of. They offer ones for carbed 502 mark v blocks that have the fuel pump bolted to the sea pump but I've found none that will fit my application. I'm going to try this gasket before I have to install the regulator. If anyone knows of one that will fit my application I would gladly try it. Thanks!
06-27-2016, 07:12 PM
#37
Registered
iTrader: (1)
It looks like Marc from BAM (earlier in this thread) would be able to get you the right one since it looks like he can recognize the good ones.
A regulator will obviously work too. Just depends on what you want to do.
BAM is advertiser and Merc dealer. Very good peep's.
A regulator will obviously work too. Just depends on what you want to do.
BAM is advertiser and Merc dealer. Very good peep's.
06-28-2016, 12:50 PM
#38
Registered
Join Date: Aug 2011
Location: Wyandotte, MI
Posts: 59
Likes: 0
Received 0 Likes
on
0 Posts
Called BAM this morning. Looks like there aren't any decent pumps and he suggested to just run a regulator.
06-28-2016, 03:11 PM
#39
Registered
Join Date: Jun 2013
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Ya that's what I figured. I just picked my gasket up huge difference from other one in thickness. Installing friday morning see what happens. Hate to install regulator on one engine when other is perfect without it.
06-28-2016, 03:16 PM
#40
Registered
iTrader: (1)
This whole thing is bullchit.
FU Mercruiser !
FU Mercruiser !
