740 Fuel leaking from Exhaust Manifold

Supersneak · 05-21-2018, 03:20 PM

I recently did a head gasket job on my 88' 740 Turbo, Had the head machined, had to remove cam to take it into the shop but all valve shims were within spec so they all went back in. Got the engine back together and into the Volv. Car wont start, i can get it to start up real quick on starter fluid, but i have a pretty substantial amount of fuel leaking out of the exhaust manifold. absolutely no idea what could be going on.

Edit: Tested injectors and none seem to be stuck open, they're fairly new and don't have more than 50 miles on them

oldschoolvolvo · 05-21-2018, 03:47 PM

I assume it ran ok before the HG job?

I’d start by making sure that the engine is mechanically timed correctly, in other words that all timing marks line up correctly.

Also make sure that no electrical connectors got swapped on reassembly. Some of them can be interchanged if you’re not careful.

lummert · 05-21-2018, 03:58 PM

Was a valve job done?

Supersneak · 05-21-2018, 04:13 PM

It was overheating before the head gasket job but other than that, it was totally sound. No valve job was done, they did a compression test and it was all good.

Dirty Rick · 05-21-2018, 05:02 PM

Gas tank over full.

If none of the injectors are leaking, how did you check?

Is the fuel pressure regulator leaking fuel into the intake?

Something has shorted one or more injectors causing them to open electrically (uncontrolled).

A Battery charger on boost and a dead battery can cause this too.

First before attempting to start.

Eliminate the excess fuel (get your nomex undies out)

ROtate the motor a couple of turns backwards so you are sure it will not hydraulic.

The less safe version is, to pull the plugs and trigger the starter to clear the motor without turning on fuel and ignition. (Nomex undies and outside near a hose for you and a fire bottle or two for the car)

Then fix the problem test and be sure fuel not being dumped.

If you have a muffler full something should be done to clear it (drill a drain hole?)

Before starting CHANGE THE OIL.

kampman · 05-21-2018, 05:07 PM

Sounds like what happened to my V70R when one of the injectors was stuck open.

Supersneak · 05-22-2018, 05:31 PM

Pulled the fuel rail and turned the engine over. Had a camera on the injectors and they seem to be putting out alot of fuel. And they stay on for a few seconds after the ignition is off. I am the only person at my shop currently so I can't get a super accurate idea if the spray pattern is normal but all 4 injectors seemed to be over spraying

aibast · 05-23-2018, 05:10 PM

My 740 turbo did that and the fault was hall sensor wire that had lost its insulation. For some reason that caused it.

Supersneak · 05-24-2018, 04:41 PM

Yeah I dropped a new distributor into it, it's the in block distributor with the hall sensor on the bottom. Where exactly was your sensor messed up on the wire

Dirty Rick · 05-24-2018, 05:47 PM

Quote:

Originally Posted by Supersneak

And they stay on for a few seconds after the ignition is off.

Should not happen, Sounds like the injectors are being powered or leaking till the fuel pressure falls off.

Supersneak · 05-24-2018, 06:01 PM

Supersneak · 05-24-2018, 06:04 PM

Quote:

Originally Posted by Dirty Rick

Should not happen, Sounds like the injectors are being powered or leaking till the fuel pressure falls off.

Could it be a result of a short in the injectors, or a bad ground?

Dirty Rick · 05-25-2018, 04:33 PM

Either the injectors are not closing or they are being kept open electrically.

Supersneak · 05-27-2018, 02:49 PM

I was having some troubles initially with the starter after the rebuild, had to replace it. what could be causing the injectors to stick open electrically?

Supersneak · 06-06-2018, 01:47 PM

So my injectors were on warranty so I swapped them out just to be sure. They are still shooting alot of fuel, what could be causing the injectors to stay open electrically?

VB242 · 06-06-2018, 09:43 PM

Bad ecu

Supersneak · 06-07-2018, 07:59 PM

Quote:

Originally Posted by VB242

Bad ecu

So that's the way it's headed. I plugged a noid light into each injector and it's very much the same story as the fuel spraying pattern. Noid light comes on when the key is in the 2 position. And throughout cranking the engine, doesn't pulse. Before we go to ECU what else could be causing the constant power

JohnLane · 06-07-2018, 08:44 PM

OP the ECU switches the ground for injectors.

Unplug the ECU. Still spraying fuel? If so look in the wiring harness. If not; ECU.

05-21-2018, 03:20 PM	#1
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	Fuel leaking from Exhaust Manifold I recently did a head gasket job on my 88' 740 Turbo, Had the head machined, had to remove cam to take it into the shop but all valve shims were within spec so they all went back in. Got the engine back together and into the Volv. Car wont start, i can get it to start up real quick on starter fluid, but i have a pretty substantial amount of fuel leaking out of the exhaust manifold. absolutely no idea what could be going on. Edit: Tested injectors and none seem to be stuck open, they're fairly new and don't have more than 50 miles on them

05-21-2018, 03:47 PM	#2
oldschoolvolvo Board Member Join Date: Mar 2004 Location: Lancaster, PA	I assume it ran ok before the HG job? I’d start by making sure that the engine is mechanically timed correctly, in other words that all timing marks line up correctly. Also make sure that no electrical connectors got swapped on reassembly. Some of them can be interchanged if you’re not careful. __________________ -Mike ~~1998 V70 T5~~ 1979 242 DL \|Feedback\|

05-21-2018, 03:58 PM	#3
lummert Board Member Join Date: Jan 2008 Location: Portland IN	Was a valve job done? __________________ Trying to understand stupid people is like trying to pick up a turd by the clean end.

05-21-2018, 05:07 PM	#6
kampman dunning-krugersquirt Join Date: Aug 2008 Location: Columbus, O.	Sounds like what happened to my V70R when one of the injectors was stuck open. __________________ 1966 220 wagon: dormant resto project 1999 S70 manual: #base, 192K 2000 V70R: 135K, deer victim/just a flesh wound 2006 V50 T5 AWD 6MT: 135K Feedback Thread

05-22-2018, 05:31 PM	#7
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	Pulled the fuel rail and turned the engine over. Had a camera on the injectors and they seem to be putting out alot of fuel. And they stay on for a few seconds after the ignition is off. I am the only person at my shop currently so I can't get a super accurate idea if the spray pattern is normal but all 4 injectors seemed to be over spraying Last edited by Supersneak; 05-22-2018 at 05:37 PM..

05-21-2018, 04:13 PM	#4
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	It was overheating before the head gasket job but other than that, it was totally sound. No valve job was done, they did a compression test and it was all good.

05-21-2018, 05:02 PM	#5
Dirty Rick Board Member Join Date: Apr 2013 Location: Cornholio, OR	Gas tank over full. If none of the injectors are leaking, how did you check? Is the fuel pressure regulator leaking fuel into the intake? Something has shorted one or more injectors causing them to open electrically (uncontrolled). A Battery charger on boost and a dead battery can cause this too. First before attempting to start. Eliminate the excess fuel (get your nomex undies out) ROtate the motor a couple of turns backwards so you are sure it will not hydraulic. The less safe version is, to pull the plugs and trigger the starter to clear the motor without turning on fuel and ignition. (Nomex undies and outside near a hose for you and a fire bottle or two for the car) Then fix the problem test and be sure fuel not being dumped. If you have a muffler full something should be done to clear it (drill a drain hole?) Before starting CHANGE THE OIL.

05-23-2018, 05:10 PM	#8
aibast Board Member Join Date: May 2005 Location: 59°19'28.19"N 24°33'17.95"E	My 740 turbo did that and the fault was hall sensor wire that had lost its insulation. For some reason that caused it. __________________ Volvo Nilsson 740 "van" 1987 - B230K automatic to M46+OD swaped ex hearse Volvo S80 2002 - D5 automatic daily eco cruiser 44mpg average

05-24-2018, 04:41 PM	#9
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	Yeah I dropped a new distributor into it, it's the in block distributor with the hall sensor on the bottom. Where exactly was your sensor messed up on the wire

05-24-2018, 06:01 PM	#11
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	h Last edited by Supersneak; 05-24-2018 at 06:06 PM..

05-25-2018, 04:33 PM	#13
Dirty Rick Board Member Join Date: Apr 2013 Location: Cornholio, OR	Either the injectors are not closing or they are being kept open electrically.

05-27-2018, 02:49 PM	#14
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	I was having some troubles initially with the starter after the rebuild, had to replace it. what could be causing the injectors to stick open electrically?

06-06-2018, 01:47 PM	#15
Supersneak Newbie Join Date: Oct 2017 Location: Oregon	So my injectors were on warranty so I swapped them out just to be sure. They are still shooting alot of fuel, what could be causing the injectors to stay open electrically?

06-06-2018, 09:43 PM	#16
VB242 A tough rowing ho Join Date: Sep 2011 Location: Virginia Beach	Bad ecu __________________ 1980 primer JDM flares franken-242DL now with 8.8, 1989 silver 780 sienna rear spring nivomat delete.

06-07-2018, 08:44 PM	#18
JohnLane Board Member Join Date: Nov 2002 Location: Northern Washington	OP the ECU switches the ground for injectors. Unplug the ECU. Still spraying fuel? If so look in the wiring harness. If not; ECU. __________________ Overkill is consistently more fun.

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