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kennyrodgers · 01-10-2016, 03:51 PM

Hi all,
I've posted this elsewhere so please forgive that but here goes.

I bought my RV in early November as an inspection failure or M.O.T failure as we call it over here.
Please bear in mind for later that as gas is so expensive over here in the UK a lot of folks fit Liquid Petroleum Gas systems thereby cutting running costs practically in half, also she'd been sat for nearly seven years.
So, I bought the vehicle and had it trailered to the testing station where it failed on a number of minor things and then my friend drove it home for me, maybe 4 miles at most. He said it ran terrible of Petrol but when the LPG system was switched on it ran great.
Forward to last week and the LPG system has mysteriously stopped working (electrical fault somewhere) so this weekend, I took it for a retest, it passed btw, but had to get it the four miles there on petrol, i was hoping to get it there on LPG but alas.
She ran terribly, no power whatsoever and she struggled to get over 30mph,anything other than feather light throttle caused backfires. Anyway, test passed and I'm thinking the injectors might be fouled so I took the air filter of and sure enough, only the left side injector was passing fuel. On closer inspection I found it was just a bad connection, sorted that out and the right side injector is now working.
The problem now is that the engine is running worse than ever, very lumpy idle where it was smooth before and major misfires and constant backfires. Also there's dark smoke at the tailpipe and she smells very rich but not quite raw fuel.
The distributor cap and rotor are new by the way.
Any pointers you guys could give me would help greatly as I'm scratching my head now. I'm fairly competent mechanically but troubleshooting something like this has got me stumped.
Thanks in anticipation,
Pete.
UK.

mbridinger · 01-10-2016, 05:42 PM

old gas?

CJ7365 · 01-10-2016, 05:47 PM

Is the check engine light on?

F4Gary · 01-10-2016, 06:16 PM

Maybe the computer needs to re-learn the mixture feedback from the O2 sensors now that both injectors are working.

kennyrodgers · 01-11-2016, 12:25 AM

Hi Guys and thanks for the replies.
It's all new gas, new filter etc .
CJ7365. The check engine soon light is intermittent. I do have a few under dash wiring problems so I'm presuming it's on.

Thanks all.

garyspang · 01-11-2016, 07:46 AM

Probably under the left side of the dash near the steering column you may find a rectangular socket with slanted end edges. I am not sure, but it may be of the OBDII type. Find an error code reader and start analysis from there.

F4Gary · 01-11-2016, 12:46 PM

Probably an OBD1. OBDII started in '96 I think.

George Schweikle · 01-11-2016, 02:12 PM

Pete,

The dual fuel conversion may have changed this, but there is a fuel filter between the gas tank and engine. If it's still there, it is on the right side frame rail.

Also, you may already know this, but here's some translation from U.S. to U.K

:

OBD means "On Board Diagnostics". OBDII is common for all U.S. vehicles, but OBD (OBD1) was specific to individual manufacturers. If you continue to have problems, it might be good to see if you can find an OBD1 scanner for your engine. 454 TBI (Throttle body injection) means it is a Chevrolet / GM 7.4Liter V8 in a P-30 motorhome chassis.

Quote:

Originally Posted by F4Gary

Probably an OBD1. OBDII started in '96 I think.

kennyrodgers · 01-11-2016, 02:46 PM

Hi all,
I only found out about the OBD1 fault codes last night so I've been today and it's showing a 12 code only, no other codes at all.
I usually disconnect both sets of batteries when I leave her for the day and I read online today that disconnecting the battery for 20 seconds or more will clear any fault codes.

Can any of you guys confirm this ??
If that's the case I'll get down there again before I start work and get her up to temp and see what happens.
Thanks again all,
Pete.

DonDee · 01-11-2016, 05:20 PM

Code 12 is all clear. Now understand OBDI is a not very smart system. Good old fashioned trouble shooting is your best bet with no codes.

Nick-B · 01-11-2016, 08:15 PM

Although it seems counterintuitive, lack of sufficient fuel pressure can cause the symptoms you describe. If this is the culprit and you say you've already replaced the fuel filter, then check the fuel pressure next. It would not be unusual for your fuel pump to be weak / failing.

CJ7365 · 01-11-2016, 08:53 PM

Fuel pressure for 94-95 TBI is 26-32

kennyrodgers · 01-12-2016, 01:40 AM

Cheers Guys, something else to consider.
I've ordered a new CTS, MAP sensor, coil, module, leads, plugs and a TBI rebuild kit. I'll fit it all one by one and test everything to see how we go.

kennersonf · 01-12-2016, 11:20 PM

One other consideration is a bad gasket between the throttle body and the manifold. It shouldn't be too hard to remove the TB (if it's the type I'm thinking of) and replace the gasket.