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Old 03-11-2016, 10:32 PM   #1
lummert
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Default Leaking Fuel Injector Symptom?

My 88 765 Turbo has a hot start problem. I've run fuel pressure tests (after installing a schrader valve) using 5 different fuel pressure regulators each with the same result. Fuel pressure immediately drops to zero as soon as engine is shut off.

I pulled the pump and swapped in different check valve. No change in symptom. Car seems to smell like gas most of the time. Sometimes the exhaust smokes like burning oil, but doesn't smell like burning oil, then it just clears up. My gas mileage around town suffers, probably related to the hot restart problem. On the highway the mileage is somewhat better, average is about 19-20 mpg.

My next step is to pull and check the spark plugs.

This is how I installed a Schrader valve on the fuel rail: I sawed off the fuel fitting that accepts the fuel supply line from fuel filter. I polished the cut 8mm fuel line with a strip of emery cloth. I installed a 5/16" compression fitting (the hole in the compression nut needs to be reamed out to fit the tube, but the ferrule fits the 8mm line) to 1/8 male pipe threads into a 1/8" female pipe thread Tee. Then drilled and tapped the the cut off fuel fitting with 1/8" female pipe threads. Installed compression fitting into on end of tee. Installed the fuel fitting in other end of tee. Installed A/C R12 type Schrader valve with 1/8' male pipe threads threads into the top of the tee. Tightened everything down and tested for leaks. Connected fuel pressure tester, no leaks.
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Last edited by lummert; 03-11-2016 at 10:43 PM..
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Old 03-11-2016, 10:58 PM   #2
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drips. drabs, puddle..
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Old 03-11-2016, 11:05 PM   #3
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Does this car have a fuel accumulator next to the main pump?
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Old 03-11-2016, 11:35 PM   #4
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Quote:
Originally Posted by nel621 View Post
Does this car have a fuel accumulator next to the main pump?
It's Bosch LH2.2. Has fuel filter next to the main pump.
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Old 03-11-2016, 11:43 PM   #5
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Quote:
Originally Posted by lummert View Post
fuel pressure tests
if regulated shop air is available, this can be used to check FPR.

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Originally Posted by lummert View Post
My next step
Pull the fuel rail out, use catch bottles, and energize fuel pumps.
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Old 03-12-2016, 12:53 AM   #6
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I had a similar problem: it was corrosion on one of the ground wires for the fuel injection system (attached to intake manifold).
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Old 03-12-2016, 12:59 AM   #7
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I had a similar problem: it was corrosion on one of the ground wires for the fuel injection system (attached to intake manifold).
Would this cause an injector to stick open?
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Old 03-12-2016, 08:49 AM   #8
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Would this cause an injector to stick open?
Negative...injectors are fed a hot 12-volts, and computer grounds them out.

Pull the fuel rail...replace o-rings
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Old 03-12-2016, 10:45 AM   #9
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Pontiacs have a injector leak down test built into the ECU. You put a guage on the fuel line, it powers up the pump for a few seconds to build about 60psi. Then it pulses each injector for a few seconds and the fuel pressure drops about 10psi. Repeat for each injector, record drop, look for discrepancy. I didn't last test I did.

Wait, how the hell would you do that on a 240!? Rhetorical question! It IS possible, but won't go into that theory.

What you could do is jump the pumps with the rail pulled and see if anything leaks out of the injectors.

Something doesn't add up here with your claim of dropping fuel pressure. What is your complaint? Does it start hard?
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Old 03-12-2016, 12:23 PM   #10
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Leaking injector can be a real bad thing,
contaminated oil will ruin motor (premature wear)
Contaminated oil will increase oil consumption and cause smoke (blue)
Contaminated oil will make motor run bad as it eats the fuel that gets cooked out of the oil
Check oil for contamination.
A cylinder full of fuel can hydrolock a motor


If your injectors are retained in the fuel rail you can pull the rail and lay the injectors on a piece of cardboard and charge the fuel system to see leaks. (fire extinguisher required, outdoors is best)
All injectors will likely not leak, usually one cylinder will have a black plug.
Leaky injectors will usually not cause an instant pressure drop, it will be gradual.

Bad/weak pump will usually present as hard cold starts

Newer pumps have a check valve that prevents back flow, worn out pump will not seal well enough to maintain pressure when shut off.
Leaking (internally) regulator will show same symptoms as bad check valve

Injector leakage is usually caused by a turdlet sneaking past the inlet screen and getting lodged in the valve holding it open. (injectors rarely wear out 500k miles)
Leakers can sometimes be saved by removing inlet screen and back flushing with air and Berrymanns spray (activate injector with a 9v battery)
Cheaper/easier to go to wrecking yard and snatch another.

Gas smell is usually an external leak or incorrectly plumbed charcoal canister (saturated)

Hard hot starting problem immediate or after soak? Have you tried open throttle start when hot?
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Old 03-12-2016, 12:38 PM   #11
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Quote:
Originally Posted by ZVOLV View Post
Pontiacs have a injector leak down test built into the ECU.
Well now, 1993, Cummins and Detroit truck diesel engines could determine which injector/cylinder was out of balance with the others, when engine was running.
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Old 03-12-2016, 01:19 PM   #12
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Default Your Next Step

You already stated your next step: pull the plugs. Sniff.

Now, when is the best time to do that? After you've let the car rest for a while, cooled down, and you've checked the oil dipstick for fuel dilution of the oil.

Then, if your sniff test is inconclusive, turn on the pumps as ZVOLV suggests. Great if you can monitor pressure while you do it. Give it 5 seconds of pump time, then disconnect your jumper and proceed with no power on. Check the plugs again with your nose.

Then, if still inconclusive, pull the rail and repeat. You should not need any more than one "catch bottle." Odds are it is only one injector flooding your car, but the intake manifold will spread the over rich mixture to more than one cylinder when it comes time to start the motor.
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Old 03-12-2016, 05:50 PM   #13
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Tried a 2.5 Bar FPR from a BMW. Fuel pressure dropped for slowly. Clamped the return hose and dead head fuel pressure was more than 100 psi. Pressure did not drop much below 20 psi. Bad fuel pressure regulators? All 4 plugs were clean. No smell of fuel in the oil.
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Old 03-12-2016, 06:33 PM   #14
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Quote:
Originally Posted by lummert View Post
Bad fuel pressure regulators?.
Test tool: Air Blow Nozzle Gun

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Old 03-12-2016, 06:51 PM   #15
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Quote:
Originally Posted by 84B23F View Post
Test tool: Air Blow Nozzle Gun

Explain how I would use this to test for bad fuel pressure regulator.
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Old 03-12-2016, 06:52 PM   #16
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I almost forgot to mention that there's no fuel in the vacuum hose to the FPR.
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Old 03-12-2016, 06:58 PM   #17
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Quote:
Originally Posted by lummert View Post
Explain how I would use this to test for bad fuel pressure regulator.
I couldn't. Manofewords won't either.

But you could see if the FPR is allowing fuel back down the return line simply by applying the clamp you used to check deadhead pressure. During rest time, of course. Remember the spec calls for only so much pressure (enough to prevent boiling of the fuel) for 20 mins. Not system pressure overnight. Check valves are not perfect.
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Old 03-12-2016, 10:10 PM   #18
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Quote:
Originally Posted by lummert View Post
Explain how I would use this to test for bad fuel pressure regulator.
I said earlier, "if regulated shop air is available, this can be used to check FPR."

Therefore, use say 40 psi air for 3 bar FPR, insert and hold rubber tipped tool into FPR's inlet-side, squeeze trigger, and see if air comes out FPR's outlet-side.

A 3 bar FPR opens at 43.5 psi
A 2.5 bar FPR opens at 36.2 psi
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Old 03-14-2016, 10:15 AM   #19
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I owe Kansas an apology. If you have shop air with an adjustable regulator, it sounds like a great way to check those spare parts in your junk box for the opening pressure.
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Old 03-16-2016, 04:25 PM   #20
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I evidently have fuel in the oil. When I check the oil level cold, oil drips from the dipstick.

When I tried the 3.8 Bar Turbo Dodge fuel pressure regulator smoke would come from the exhaust when sitting at a traffic light.

This morning I tried another 3 Bar fuel pressure regulator with no noticeable difference from the other 3 that I've tried.

While at my Friends junkyard this morning I found a set of Bosch 4 hole injectors in a late 80s to early 90s Pontiac Bonneville SSE Supercharged.

Bosch 0 280 150 934 (WHITE TOP)
@43.5 psi (3 Bar)
29.3 Lbs/hr
307.9 cc/min
221.5 grams/min

EV1 feed
High Impedance

Funny that I'd find OE Ford injectors in a Buick 3.8L supercharged V6. These injectors have the same specs as Ford Racing B302 injectors (Bosch 0 280 150 945)

Bosch 0 280 150 945 RED TOP Specs:
30Lbs/hr 320cc/min @43.5 psi.

Bosch 0 280 150 934 WHITE TOP Specs:
30Lbs/Hr 320cc/min @43.5 psi

Last edited by lummert; 03-16-2016 at 04:43 PM..
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Old 03-16-2016, 04:40 PM   #21
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Well then you'll be wanting to delete the resistor pack to use those.

Here's a link if you're not up on how to do that.

Hope that fixes it for you. But if your FPR is fuctional, doesn't seem like much else can be causing that...
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Unique for sure.
I don't think anyone is going to tell you it looks bad.
Kinda can't go wrong under the hood.
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Old 03-16-2016, 08:44 PM   #22
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Quote:
Originally Posted by lummert View Post
Bosch 4 hole injectors in a late 80s to early 90s Pontiac Bonneville SSE Supercharged.
Injector location in this 3800 engine is inline with intake port, like Volvo, so the spray pattern should be the same. I'd test the spray pattern before installing, unless these came from a recently retired vehicle.

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Old 03-16-2016, 08:57 PM   #23
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The Ford injectors are in. I checked for leaking injectors after pulling the fuel rail. Not one drop of fuel from the injectors with the fuel pump relay jumped. I then checked for leaking with the 3.8 Bar fuel pressure regulator, still no leaks.

I installed the Ford Injectors and adjusted the AMM. The AMM adjustment ended up being nearly the same as with the stock injectors. Car runs smoother and has more seat of the pants feel.

Next thing is get a fuel pump check-valve. The used check-valve I recently installed has to be bad.

I bypassed the resistor pack, but a permanent solution for that is needed.
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Old 03-18-2016, 06:53 PM   #24
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If I had known that Bosch 4-hole 0 280 150 934 injectors would cause my 88 765 Turbo to get 25 mpg I would have done this swap years ago.

Don't everyone run out and hunt these injectors at the same time.

Hint: they were OE in Buick V6 3.8L V6 Supercharged used in 91-95 Buick Park Avenue, 1995 Buick Riviera, 92-95 Olds Ninety Eight, and 92-95 Pontiac Bonneville.
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Old 03-18-2016, 07:02 PM   #25
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Youre getting the mileage its supposed to be getting.
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3/4", make everything as heavy as possible for no reason. It's also 4:1 compression ratio because that's how cosworth did it in 1978.
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