capt_furious Posted May 26, 2008 Share Posted May 26, 2008 Carried over from the L6 section: Car is a 260 with an L28 and 5 speed running round-top SUs. I've been having a low pressure issue for about a week / 2 weeks now. Not too many issues when cold(pressure builds and holds right away at start), but once the car is warm, pressure is about 1/2 to 2/3rds what it should be. I've got about 60 psi at cruise when the car is warm. It takes a while for the pressure to build when warm, no problem when cold. The oil is about a month old, about 3 weeks ago I had the on-block fuel pump go bad and spray the engine bay with fuel from between the body and top cover. I might have got fuel in the oil, but can't tell. I assume it will have evaporated off by now. The pump is bypassed right now and I'm running off of a Napa-bought electric Carter replacement(3-5 psi rated) at the tank(car is a 260, Carter pump replaced the stock electric pump). No smoking or running issues, car seems to run all right. Little bit of lifter / valve tap on startup occasionally that settles down after running for a bit, could be a lousy adjustment job by the shop I took it to(which I'm having them fix this week). Do an oil change and replace the pump? Just an oil change? Am I seriously screwing up my motor by running it with (somewhat)low pressure? It's my daily and I don't have many options for putting it down, so I've kept an eye on it and carried on. Quote Link to comment Share on other sites More sharing options...
Nigel Posted May 27, 2008 Share Posted May 27, 2008 Do you have the OEM oil pressure gauge and sending unit? How do you know what you're reading is accurate? Perhaps you should try an aftermarket gauge and sender to confirm... Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 27, 2008 Share Posted May 27, 2008 Your oil pressure is fine. I replied to your other post as well. Mechanical Gauges only for diagnosis. Do not trust the dash gauge. Quote Link to comment Share on other sites More sharing options...
capt_furious Posted May 27, 2008 Author Share Posted May 27, 2008 I'd assume it was the sender or gauge but A) the gauge has not had issues with the previous motor and the sender(assuming the issue is the sender) was working fine up until recently. The behavior seems strange as well, to have plenty of pressure when cold and not when hot. I'll check the connections. Thanks, both of you. Quote Link to comment Share on other sites More sharing options...
Nigel Posted May 28, 2008 Share Posted May 28, 2008 I'd assume it was the sender or gauge but A) the gauge has not had issues with the previous motor and the sender(assuming the issue is the sender) was working fine up until recently. That's no gaurantee that they're working now The behavior seems strange as well, to have plenty of pressure when cold and not when hot. Cold oil is thicker and therefore builds more pressure, so this is not unusual. I'll check the connections. Sounds like a good start. Good luck, and let us know how it turns out... Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 28, 2008 Share Posted May 28, 2008 Screw a mechanical pressure gauge into the side of the block where the sender goes and take some readings. That's how I determined my sender went bad. My dash gauge reads about 3/4 up when cold and 1/2 when hot while driving. At idle, hot, it runs less than 1/4 on the gauge. The engine burns oil but runs awesome (does not affect oil pressure). Ask EvilC with his LS1 that thinks my old L28ET might be quicker. Waiting for EvilC to read this.... Seriously, your engine is probably FINE. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 28, 2008 Share Posted May 28, 2008 At idle, the L will survive in stock form for a looooooong time with only 3 to 5 psi at stock idle speed of 750rpm. The stock gauge will not even read that low! This is not a Chevy where you have 43psi at idle... Quote Link to comment Share on other sites More sharing options...
capt_furious Posted May 30, 2008 Author Share Posted May 30, 2008 Got it tested. Bad sending unit. Thanks for the peace of mind! $40 fix. Quote Link to comment Share on other sites More sharing options...
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