Fuel PSI issues!
- Thread starter YB 468
- Start date
What size fuel lines are you running from the fuel tank to the pump and then to the regulator, then what size fuel lines are going from the regulator to the carb. How many horsepower are you making? Are the fittings right angle fittings or fittings that have a bent tube? It all affects the outcome.
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southwind854
New member
Have a few ?. First have you done a full power run plug check. Second what impeller are you turning. And third is it cutting out. From what you have posted you have gone threw all the proper checks. Only reason I ask ? Is I had a similar issue and it's was ignition related not fuel.
73 Sanger Flat
Active member
Make sure your vent line is open .. It must get in as much air as you take out in fuel .. A dirt dopper or anything could have plugged the end of it ..
Is the engine laying over when the fuel pressure drops ?
Try and by pass the water separator and see if the pressure still drops
Also try and check the pick up tube in the tank , could be broken inside and sucking air in hard acceleration . Switch tanks and see if it does the same on both tanks .. If you are drawing from both tanks at the same time . I suggest to seperate them with a fuel valve . Run one tank at a time and then switch when one is almost empty .
Is the engine laying over when the fuel pressure drops ?
Try and by pass the water separator and see if the pressure still drops
Also try and check the pick up tube in the tank , could be broken inside and sucking air in hard acceleration . Switch tanks and see if it does the same on both tanks .. If you are drawing from both tanks at the same time . I suggest to seperate them with a fuel valve . Run one tank at a time and then switch when one is almost empty .
Dookie, Put up some picks of the fuel system from the tanks out so they can see what you have, I don't have any pic's of that area, I know you have plenty supply to the pump. Hears one thing that concerns me, does that pump "require" a regulator? Some do, Some don't. if it is a none regulator type then the regulator needs to come out of the system.YB 468 said:
southwind854
New member
What Rpm was it turning previously before the issue started. And does the tank out let fitting have anti siphon valves or strait flow. And what pressures were you running previously.
Tanks are coustom built, feed from bottom, The Fuel system is 1/2" from the tanks to the filter, 3/8 from the filter out, Ball valves control the flow, Burns one tank at a time, the filter is a 2 quart filter, there is enough capacity in this system to supply a 2,000 HP Diesel! I am thinking that the pump he replaced was bad and required a Regulator and the new one does not, Will have to wait till he gets back on here to confirm what Pump he installed, I did not look at the part number.Brazos River Rat ( Billy ) said:
southwind854
New member
Ok first thing I would try is take a line from one tank straight to the pump and do a run to see if maybe it's a flow problem. Second this sounds like mine when I switched to corn fuel. I went electric to a AEI 1000 electric pump. And when the pump was replaced was there wear on the pump rod ends.
texas ultra
New member
Check your fuel tank fittings. Do you have an anti-siphon valve on the fuel tank connection. It is a real light spring and check ball that prevents fuel from siphoning from the tank in case a line comes off. They give just enough restriction on the suction side to cause all sorts of problems. One season on my boat everything was fine. First time out next year the issues came up. Changed everything and still could not get rid of problem. Finally removed these fittings everthing was back to normal. The fitting looks like a normal 90 but usually has a small screw on the head. They are coast guard required but cause problems on engines needing high fuel flow.
texas ultra
New member
I changed fuel pump, lines, fuel selectors, added vent lines, upgraded ignition, changed carbs, played with jetting, ignition wires, plugs and more. The fittings look just like 90 pipe to hose barb fittings. Now everyone I talk to about them tell me they cause so many people trouble. Ask them if you should remove them they say that can't tell you to do that, but they are problematic. My tanks are made by Imco and all their tanks come with them. Any boat manufacture after a certain date (I am not sure of date) will have them by law. I ran all season with this problem with an intermittent miss on the top end. The detonation wound up breaking a piece off one of my Mahle pistons where the intake relief is above the rings. Luckily the piece escaped out the exhaust without tearing anything up. Finally changed the fittings and the boat ran like a bat-out-of-hell. That day the felpro marine head gasket blew. The gasket was weakend by the previous detonation. Ask CP Performance for better head gaskets and they said if I blew them, must of had a detonation issue. Save yourself a lot of grief and pull the fittings and examine! Sounds just like my problem. I am an aircraft mechanic and inspector and have been building motors since I was 13 years old, consider myself very knowledgeable and this stumped me. Felt like a fool afterwards.
I know EXACTLY what you are talking about, I stumbled across them while working on a Boat with an outboard, That thing nearly kicked my A$$ all becuse of the very same 90% check valve you are talking about! I am fairly certain that this system does not have them as this is all 100% custom built, tanks and all by a fast boat builder that would not have resticted the fuel in any manner BUT it is possible that the filter housing has a check valve in it, that was added to the sysem after the fact.texas ultra said:
southwind854
New member
Notta on the pics