No start when warmed up - M20 B25

[e30vert]

1988 BMW 325ic. - B20M25 Engine
Reassembled engine after powder coating parts / chrome ,etc.

New Intake Manifold Gaskets
New Exhaust Gaskets
New Valve Cover gasket
New Distributor Cap / Rotor
New Silicone Coolant Hoses
New Performance Aluminum Radiator with Electric Fan Wired and functional.
New CPS - Metal Canister style - 540 Ohm reading on CPS Pins which appears to be within specification.
New battery - Charge @ 12.45 volts.
Fresh Oil 5/30 European Blend Mobil 1
Fresh Coolant. 50 / 50 premix Penzoil
Both at proper levels and coolant bleed done to remove air bubbles
New Fuel Filter and upper fuel filter hoses all with hose clamps secured
New Elbow from Throttle Body. Large one and smaller one
New Valve Cover breather hose with new hose clamps.
All torque specifications correct. i.e. Valve cover nuts ,etc.
DME has performance chip installed that worked great when it was installed and I don't have any reason to doubt it working correctly now.
Spark Plug Wires reused.
Installed in correct order on Distributor Cap and plugs - Speed Sensor wire is on Plug Wire to # 6 cylinder and it should be.
Spark Plugs do show signs of oil fouling and deposits. Car sat for many years so I had to spray some Marvel Mystery Oil in each cylinder and rotate the engine by hand using a 22 mm wrench on the crankshaft to break the pistons free and not induce cylinder wall or piston damage.
Fresh Ethanol Free Gasoline added and I could not detect a single drop of fuel in the system before I added some.


When first reassembling I installed CPS sensor on Speed Sensor Harness Connector and vice versa so engine would not start. Caught mistake and swapped em. Engine started with high idle. Really high like 1800 RPM. Found out I installed the big wire from the Alternator (RED) to the wrong starter post and the Alternator would not charge the battery or operate the internal electrical systems. Pulled the big RED wire off and doubled it up on the post with the Large BLACK Wire _Battery Wire on the starter - Farthest large lug on the Starter away from the engine block.

Now Alternator charges as it should.
No more super high idle.
Adjusted idle to about 800 RPM
Still running a bit rough and there was valve tick so I figured I would adjust valves.
Adjusted Valves incorrectly at first by using the .025 feeler gauge. Ran the engine at startup idle and ticking was worse so I corrected the valve adjustment and used the .010 in feeler gauge.
Quieted the valve ticking a bit.

Pulled Fuel Pump Relay, O2 relay, and Main relay. Sanded down all pins for better contact and then added dielectric grease on terminals before reinserting



Checked Idle Control Valve (ICV) and Multimeter reads 20 ohms from center pin to outer pins and 40 ohms across from the outer pins. Seems within spec.
I have adjusted the TPS and measured that it has continuity when throttle is closed -idle (middle pin and right pin) and when wide open throttle (Middle Pin and Left pin)

Added Cold Air intake (KA Motors)
Pulled battery cable over night so the DME could relearn the mapping with the Cold Air intake after start up.



Ive got to the point where the engine starts right up when cold. Then idles with a bit of side to side shimmy. While looking at the opened hood it moves back and forth ever so slightly.
Idles constant at approx. 800 RPM with light fluctuations.

Then when manipulating the throttle from the engine bay and giving it quick throttle it does not respond quickly and will sputter and sometimes recover and other times the engine dies.


Then when reattempting start of the engine after warm up it will no longer start and just cranks.
All fuses checked in Fuse Box for continuity and they are good.
Battery Clamps tight.

Did a cold compression test and all cylinders were good except # 5 was a bit off and 6 was farther off

1- 140 psi
2-142 psi
3-139 psi
4-139 psi
5 -120 psi
6 -115 psi

Added a squirt of Marvel Mystery Oil to Cylinder 5 and got up to 125 psi
and also oil squirted # 6 and reached 120 psi.

Pulled plug on MAF while at idle and engine begins hunting for proper fuel / air mixture. Reconnect - idle smooths out.




Cylinder 6 concerns me , but no smoking out of tailpipe and if the rings are bad in cylinder 6 then they seem passable for the short term.





Ive got new plugs on order.
Spark Plugs will be replaced on Friday when they arrive. NGK ZGR5A

Things I have been considering next are smoke test and replacement of the Spark Plug Wires and potentially the Main Relay.

Thoughts? Troubleshooting techniques I may have missed?

[tomstin]

You made a lot of changes, so a lot of variables to deal with. Time to get back to basics. When it doesn't start, do you have spark? Pull a plug, put the wire on it, ground it, do you get spark? If you have spark, do you have fuel pressure? A lot of auto parts stores you can rent / borrow a fuel pressure gauge. Check the fuel pressure at the regulator. I suspect you are missing one of the two.

[jbontke]

tomstin is right, start with the basics. Also, just because you have new parts doesn't mean they are not free of defects. I bought new cps/speed sensors for my car, was having trouble on hot starts. They metered ok when cold, but out of scope when hot. I bought OEM cps/speed sensors and they worked fine. Parts quality is important as well.

[e30vert]

Great Advice as far as how to proceed. I borrowed a Fuel Pressure Test kit from the local Auto Parts store and hooked it up with a brass T included in the kit before the Input to the Fuel Pressure Regulator. Picture included of connections. My new run of Fuel Hose felt kinda squishy in the sun and pliable.

When I cranked the engine it did not start of course as the vehicle had already warmed up.
The pressure on the gauge builds and builds right over the last limit on the gauge 100 psi and then when no longer cranking the pressure recedes quickly and does not hold.
Video link to process here - https://www.youtube.com/shorts/w3b8QH2qy4Y

I know that the fuel pump only pumps when the ignition is in the cranking position unless one pulls the fuel pump relay and jumps pins 30-87 with the key in the on position , but shouldn't there be fuel pressure that "holds" pressure?

Does this mean that my pressure regulator for the fuel or fuel pump is suspect?

[e30vert]

I'll do spark next. Should I also place the Fuel Pressure Tester inline on the Fuel Rail connection to see what the pressure reads and if it "holds" pressure?

[e30vert]

I hooked up the Fuel Pressure Gauge to the Fuel Rail fitting "inline" with the T adapter. Pulled the Fuel Pump Relay, turned the ignition to the ON position and jumped pins 30 and 87. I heard the fuel pump engage and then the Fuel Pressure gauge went all the way up to over 100 PSI. I unhooked the jumper wire to dis engage the fuel pump and the pressure settled down to 3.1 bar approximately. Video of process here - https://www.youtube.com/shorts/QwzSfiPpLtw

Pressure drop to 2.8 bar after 15 minutes.

[digger]

pressure should be checked on the pressure line input into the fuel rail and be around ~38psi idling and ~43-45psi (3b) WOT. if you mix the lines between the fuel rail and FPR so the pump is pressurising the other side of the FPR it will fubar the FPR.

you are either checking pressure on the return side or you have the lines swapped.

Either way there should not be anywhere 100psi with a functional FPR.

[e30vert]

Good points! When I reconnected the fuel lines I jumpered the fuel pump relay with the key in the ON position and watched to see which hose was pumping gas at a higher rate. The hose that was I connected to the fuel rail near the top of the Intake Manifold as I figured that this was the hose coming from the fuel pump in the tank.


I checked pressure on both hoses as Indicated in the video links I provided. First I checked where the hose connects to the Fuel Pressure Regulator and then the second video is checking the Fuel Rail Connection Hose. Both times I just plumbed the T fitting inline with the fuel hoses.


Could I have switched up the hose . Well I guess so. Whats a good way to determine which is which as I dont want to connect the wrong hose to the Fuel Pressure Regulator and also the Fuel Rail after I replace the Fuel Pressure Regulator.

Im going to replace the Fuel Pressure Regulator as I am sure its old to begin with and I dont want to screw it up with pressurizing it with output from the Fuel Pump.

[digger]

you pull the hoses off, jump the relay to start pump and see which hose the fuel comes from and connect that line to the fuel rail and the other hose to the FPR. if you checked pressure on both hoses and got 100psi the the FPR is bad or there is a blockage on the return line or both

[e30vert]

you pull the hoses off, jump the relay to start pump and see which hose the fuel comes from and connect that line to the fuel rail and the other hose to the FPR. if you checked pressure on both hoses and got 100psi the the FPR is bad or there is a blockage on the return line or both

Gotcha! Im going to try and blow into what I think is the return line that heads into the fuel tank and see if I can or if there is a ton of resistance . If there is resistance perhaps I can run some compressed air at a low PSI through that hose . This seems like it should work?

[e30vert]

I pulled the fuel line off that I have connected to the Fuel Pressure Regulator and I cannot blow through it. I left the Pressure Tester connected to the fuel Line that I have connected to the Fuel Rail Hose.

I then jumpered the fuel pump relay and the hose that was connected to the Fuel Pressure regulator did not spit out any fuel. The pressure gauge connected to the Fuel Rail DID raise in pressure and then some fuel was spit out of the Fuel Pressure Regulator where the hose would connect to.

It seems that I have the fuel hoses connected properly and the inability to blow through the hose connected to the Fuel Pressure regulator seems odd. Or is that normal?

[digger]

put the gauge onto the pressure side between pump and fuel rail. Add a new hose from FPR into a bucket and try that. if the pressure is incorrect (still high) and hardly any fuel comes out the FPR is faulty

[e30vert]

Pulled the gas cap off and tried to blow into the line that was connected to the fuel pressure regulator and I cannot blow through it.

I could have a clog on the return line side . Perhaps?

[digger]

Pulled the gas cap off and tried to blow into the line that was connected to the fuel pressure regulator and I cannot blow through it.

I could have a clog on the return line side . Perhaps?

Does the FPR behave itself with the test from post#12?

[e30vert]

Pressure Gauge is still hooked up to the Fuel Rail Hose and I will pull the hose off the Fuel Pressure Regulator and place another hose on it that exhausts into a bucket tomorrow morning and report back..