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I have built an A+ 1310. Fresh bore, crank turned 10/10 SW 5 cam and new AP oil pump. On test stand with everything connected I primed the oil pump then spin engine without plugs on starter. Oil pressure comes up to 40 psi. Stop cranking and the mech. gauge slowly drops to zero. Wait a couple of minutes and crank again and no oil pressure. Even with a freshly charged battery it won't pick up OP again. The tranny was completely rebuilt with a new COP. Charge the battery and prime again and it does the same thing. Any thoughts? Thanks Steve (CTR)

Steve. Have you tried a different gauge? I don't like the fact it only comes up to 40psi unless that's where you want it. Its too low for cold oil.

At first that was a concern but I had just removed another power unit that was running at 65 psi. I pulled and checked the relief valve. My thoughts are that there is a leak on the pick up side and that is why it won't hold a prime. If it can't pick up oil correctly it would not make full pressure. Got to find out can't send it out this way. Steve (CTR)

CooperTune wrote:I have built an A+ 1310. Fresh bore, crank turned 10/10 SW 5 cam and new AP oil pump. On test stand with everything connected I primed the oil pump then spin engine without plugs on starter. Oil pressure comes up to 40 psi. Stop cranking and the mech. gauge slowly drops to zero. Wait a couple of minutes and crank again and no oil pressure. Even with a freshly charged battery it won't pick up OP again. The tranny was completely rebuilt with a new COP. Charge the battery and prime again and it does the same thing. Any thoughts? Thanks Steve (CTR)

Sounds like an air leak on the suction side. Possible causes:
No O ring or damaged/misplaced O ring between transmission and block
Missing gasket between oil pick up and transmission
Missing or damaged gasket between cover plate and oil pick up pipe and outside of transmission case
Too long bolts used for oil pump and pump not clamping gasket onto block
Oil pump bolts not tight and not clamping pump to block
Damaged oil pump gasket

I'd agree with that. I pulled the power unit from test stand and placed on engine stand. Removed the hat, flywheel and clutch housing. Split engine, tranny and the O ring was there but the gasket was wet both sides. I cleaned the pan rails and installed a new O ring and gasket. Put it all back together and it did the same thing again. Pulled hat, flywheel and housing. Removed the oil pump. The gasket looks fine so I stripped the oil pump and it all looks good. I placed a tapered clear plastic tube in the pick up side hole in oil pump recess sucked gently and the oil came right up. I have oil pump gaskets in bags of 10 none seem to be well made. I may set up to run pump on starter with engine on assembly stand. Built my first Sprite 948 in 1965 and average 3 to 4 a year. This is something new for me. Steve (CTR)

I'm not crazy about this AP pump. The mounting side is all scalloped out and the steel cover is held on with two bolts and the two mounting bolts. Close inspection of the cover shows a witness mark 3/4 way around. There is a area between two of the bolts that don't show any contact. Also noticed when I removed the pump gasket it was only stuck to the block in the two mounting bolt areas. I have never used a sealer on the pump gasket. I will select fit a gasket and another new pump today and give it a try. Steve (CRT)

Could the oil pump bolts be bottoming out in their holes? I have seen this a few times.

M

If you had pressure then none I'd be taking a close look at the relief valve 1st

i had a similar problem, and it also was the gasket , i was using a turbo pump and it built up 100 psi,, then nothing, it was due to the gasket blowing, replaced with standard pump, and new gasket, nice steady 60 psi on a fresh engine, fine ever since.

also are you using a standard spring and plunger in your relief valve, i was using a heavy spring and ball bearing , and was strongly advised not to use it,

sounds like the your oil pump face is not flat,

I had an issue not dissimilar it turned out the oil pump drive was not long enough but on initial start up had some type of interference fit with the cam drive pin but only when cold as the unit warmed the oil pressure dropped off to zero ,I took the oil pump back to the very red faced engine shop ,it was giving similar symptoms to yours hope this is useful good luck and IIRC on another unit swaf was jamming the pressure release valve giving dropping pressure

Try some blue marking.

Do a search on Turbominis, seems the Evolution pump is the easiest solution.

I tend to run a tap into the bolt holes then run the bolts in finger tight to the bottom. Then measure the under head length. It turned out to be 1 1/8" and the pump body with cover is 1 1/4'. This leaves about 1/2 " thread engagement. After removing the back cover and noticing the witness mark 3/4 way around I glued some fine emery to glass. The pump body where the cover rides shows tool marks like a fly cutter. Don't know if it was loose in the fixture or what but lapping shows a low spot between one cover bolt and one mounting bolt. I installed another new pump ( different brand ) got it all back together but no time to test before dinner. Looking forward to a good start tomorrow. I also pulled the OP relief valve first thing and double checked that it was sealing and all parts were in there. I could get OP every time I primed the pump at the rear of block but only once per prime. Thanks for your interest I will report back tomorrow. I could have lapped the housing till square and if it did not pinch the rotors still use it. Steve (CTR)

All right, three sets of gaskets, two oil pumps and assembly three times. I now have oil pressure almost as soon as the starter engages. Running the OP is 55 lbs. One washer behind the spring brought it up to 62 psi. running. I lapped the first pump housing and cover till I had full contact. I have not measured clearance but it does not pinch. Anyone know the minimum clearance allowed. I have used a jewelers files to clean up the pump ports, may as well set it up and give it a try on the next build. Steve (CTR)

CooperTune wrote:I'm not crazy about this AP pump. The mounting side is all scalloped out and the steel cover is held on with two bolts and the two mounting bolts. Close inspection of the cover shows a witness mark 3/4 way around. There is a area between two of the bolts that don't show any contact. Also noticed when I removed the pump gasket it was only stuck to the block in the two mounting bolt areas. I have never used a sealer on the pump gasket. I will select fit a gasket and another new pump today and give it a try. Steve (CRT)

These are the steel backed pumps, that have the cover fixed with two X head screws (that always seem over tightened), 4 lobes on the main rotor?

I always like to take the Oil Pump apart on removal from an engine and I've noticed in every one of these pumps without exception that same witness marking, though it does vary from 1/3 to 3/4 the way around. I'm not certain just why they do that as measuring them in a real world situation (ie, fixing bolts fitted and torqued) is not easy and I suspect that while they come out of the box true enough, they distort on fitting. I've noted the almost wafer thin gasket contact they have in a few places, but - touch wood - I've not had a problem to date, none the less I think your experience here might just be a wake up call for the rest of us.

I'm also just wondering about what role the gasket itself may have had in all this for you. Not just the thickness of the gasket, but it's strength and compressibility. The gaskets I've been using for years are locally made so would be different to what most others here have been using.

I don't know what the minimum clearances need be, I've never bothered to measure them. When after taking the pumps apart and seeing how much has gone through some of the pumps, and general wear in them yet they still hold good pressure, it's fairly clear they are well over rated in capacity their design. While I haven't measure them, I do take the new pumps apart for inspection, cleaning and also 'feel' them. I'm also wondering if on fitting, the cover distorted away from the pump body, there's no seal between these parts and I've often marvelled at how well they appear to seal against each other. Again, I feel this shows how over rated (in capacity) they usually are. I think t fair to say that in your case here, there was a leak somewhere on the inlet side.

I agree I have always taken pumps apart after service to look at the condition. I used to take new pumps apart to clean and lube before assembly. The low spot was in the inlet side of the pump. Yes there was an air leak and it would loose prime as soon as it stopped spinning. I also have always wondered about the pump gasket but never had an issue before and that goes back a long time. A local shop cuts gaskets with their water jet. Not sure how that would work with such thin material. Have to look at it as a learning thing. Now there is one more thing to check carefully during assembly. I have two completed power units going home for Christmas. One in the car the other on a pallet. Steve (CTR)

PS anyone running a HIF 44 on a 1310 with 10.2 CR and SW5 cam? I'm running a BDK needle and it's just off the scale above 16.5 to 1. I plan to order a BAM today any suggestions on a needle that has worked for you?